THE LIFE OF THE M OLLU SCA

B B OODWARD ar c . . gy , . OF THE n m su MUSEUM ( NATURAL m sro m r) PAST-PRESIDENT o n THE MALACODOGIGAL SOCIETY OF LON DON

WITH THIRTY-TWO PLATES AND A MAP

TD M ETHUEN C O . L .

C . E SSE X STR E E T W. LON DON

PR EFACE

T HE object o f the present work is to give a succinct account o f what is known concerning the life o f that branch o f the animal kingdom to

a l an d Cu which the Sn i , the Oyster , the ttlefish — C belong the MOLLUS A.

E a a ha heref re speci l ttention s, t o , been given to their

a an d a f history , rel tionships, everyd y li e (ecology),

a m with only gener l notes on their anato y, classifica

t o an d s u . i n di trib tion , etc

The numerous illustrations it is hoped will prove

M u helpful to students . any fig res have been specially

M . M . bu f drawn by iss G Woodward, t most o them

’ r . P . first appeared in the late D . S Woodward s

M u o f M a a a n an al the ollusc , the origin l dr wings a d engravings fo r which are in the possession o f the

a are writer . Cordi l thanks due to the Trustees o f the British Museu m fo r their courteous permission vi THE LIFE OF THE M OLLUSCA to reproduce illustrations from their publications or taken from specimens on exhibition in the Natural

M u History use m . Other illustrations have been

Mr M . kindly lent by . W. Webb , F. L . S.

a u N a a H M To his colle g es in the tur l istory useum ,

Mr. E . . A an d Mr . Smith , . G C . Crick, the author is indebted fo r valuable assistance in regard

s o f a to point nomencl ture. CHAPTER PAGE

INDEX

L IST O F IL LUSTRATIO N S

PLAT E

I TH SH O A OF . E ELL (IN SECTI N) AND NIMAL THE

’ P N U US N autilus om ilzus EARLY A TIL ( p p ) .

II. V O S G S O O S S OW A L S ARI U A TR P D , H ING THE NIMA C W RA LING.

D G K F OF III . IA RAMMATIC S ETCHES O THE STRUCTURE THE G S N OUS S OF M O US ILL AND ERV SY TEM LL CA . D RAWIN G S OF THE D IFFERENT FORM S OF THE M S R U OF M O S ANDIBLE AND AD LA LLU CA , ETC .

IV D G A . IA R MMATIC SKETCHES To ILLUSTRATE (a) THE TO S O OF G S O O BO b T T R I N THE A TR P D DY , ( ) HE RAN SITION FROM A FLAT -COILED GASTROPOD SHELL To

R OR A - H S ONE c TH A IGHT LEFT ANDED PIRAL , ( ) E M O S B S d T ANTLE PENING IN IVALVE , AND ( ) HE D F F S B IFFERENT ORM S O GILL IN IVALVE S .

V D FO S OF CO G OF A U . IFFERENT RM ILIN , PERT RE , AND G S O S ORNAMENTATION IN A TR POD SHELL .

VI TOFOGRAFHV OF G S O O SH S FO M O . A TR P D ELL , AND R ATI N OF C US U U S OF N A TI CA ALL IN THE MBILIC .

VII. NO P O G S O O TCHED AND ERF RATED A TR P D SHELLS . SHELL STRUCTURE AND R EMOVAL OF PORTIONS OF

THE SHELL .

VIII V OUS D S FOR EX E . ARI EVICE CLUDING NEMIES FROM G S O O SH S A TR P D ELL .

V S FO F IX. ARIOU RMS O SHELL AND ANIMAL IN THE A PO O O B A O HO C ( ) LYPLAC PH RA , ( ) PLAC P RA , AND ( ) P OSO D O OG OSS R O OSS R BRANCHIA ( C L A AND HIPID GL A). ix x THE LIFE OF THE MOLLUSCA

PLATE V O U S FO S OF S S G S O O X . ARI RM HELL IN THE A TR P DA PROSOBRANCHIA (TE N IOGLOSSA).

XI V OU S FO S OF S S G S O O . ARI RM HELL IN THE A TR P DA PROSOBRANCHIA ( R HACHIG LOSSA).

XII V OU S FO S OF S S G S O O . ARI RM HELL IN THE A TR P DA P T x G LOSSA H T ROSOBRANCHIA ( o o ), T E ECTI

H OF A S OF N U . BRANC IA , AND THE NIMAL DIBRANCHIA

III V OU S FO S OF S S PU O . X . ARI RM HELL IN THE LM NATA

- V A O E S U Testacella sm tulum . XI . W RM ATING L G ( ) XV U U S OF S O O . STR CT RE AND HELL THE CAPH P DA ’ - (ELEPHANTS TU SK S HELL S).

V OUS BIVAL VE s S HOW A S X . ARI , ING THE NIMAL E TENDED XVI TO O OF B S S . P GRAPHY IVALVE HELL .

VII V OU S FO S OF B S S : P O O X . ARI RM IVALVE HELL R T ERAN H A F C I AND ILIBRANCHIA .

I V OU S FO S OF B S S : EULAMELLI XVII . ARI RM IVALVE HELL A OS B SU BRANCHIA ( . TRACEA, . BMYTILACEA, AND C T ' . ELLINACEA).

XIX V O S FO S OF B E S : EULAMELLI . ARI U RM IVALV SHELL

D V E . C BRANCHIA ( . ENERACEA . ARDIACEA , F C G M . HAMACEA , AND . YACEA).

V O S FO S OF B S : E ULAMELLI XX. ARI U RM IVALVE SHELL H D M A A I H A E S CE . A BRANC IA ( . AND NATINACEA) S AND EPTIBRANCHIA .

XXI C O FO OF A . EPHALOP D STRUCTURE AND RM NIMAL , ETC .

II V IOUS F S F C O O XX . AR ORM O THE SHELL IN EPHAL P DA

TETRABRANCHIA (N AUTILUS AND AMMONITES) .

III R S O O OF A OF B S . XX . E T RATI N NIMAL AND SHELL ELEMNITE

IV FO S OF B ITS XX . RM THE SHELL IN THE ELEMNITE AND D S S E CENDANT .

XXV V US F S F I . ARIO ORM O THE ANIMALS AND NTERNAL S HELLS OF CEPHALOPODA DIBRANCHIATA (CUTTLE S H PE N- AND-INx-F SH O O U S FI , I . AND CT P ).

VI V O S FO S OF SE - XX . ARI U RM A BUTTERFLIE S (PTEROPODA) H O O W S S F P AND ETER P DA , ITH HELL O ELAGIC FR Y OF M O S - LLU CA , AND SURF DWELLING P UL O S M NATE , ETC . LIST OF ILLUSTRATIONS xi

PLAT E

VII FE T KS OF S . XX . EDING RAC NAIL AND SLUG

- - VIII L H S O OF CO I MAGIL US . XX . IFE I T RY THE RAL NHABITING ExAMFLE OF F OUS FO MOF OU CO A IBR R TER VERING , OR PE OS OF M O S Xeno RI TRACUM, AND A LLU C ( pho m) THAT BUILDS INTO ITS SHELL FRAGMENTS O O S CO S F S O S. THER SHELL , RAL , AND T NE

I T M O S E OS . XX X. YPICAL LLU CAN MBRY DIAGRAMMATIC SKETCHES OF THE STRUCTURE OF

M O S E S . LLU CAN YE , ETC

- E S EGG C SU S . OF SO G S O O S XXX. GG AND AP LE , ETC , ME A TR P D . F T K B S SECTIONS O SOME HIC IVALVE SHELL . F F O VARIATIONS O THE O T IN BIVALVE M OLLUSCA .

I CO O G S C W S OW XXX . MM N ARDEN NAIL RA LING . AND H ING F THE M OTION OF THE OOT .

II E FO S OF G ASTROFOD S S XXX . CCENTRIC RM HELL , AND ExAMFLES OF THE ExTE RN AL R ESEMELANCE BETWEEN SHELLS OF WIDELY DIFFERENT FO RM S

OF M OLLUSCA .

MAP.

All the Plates (except Plate I f ronti spi ece) and the Map are at the and th book of e .

THE

LIFE O F THE M O LLUSCA

CHAPTER I

GEN ERAL IN TRODUCTORY

HELLS have ever been attractive Objects owing to the beauty o f form an d Coloration displayed

f m n u are by so many o the , a d tho gh they no longer fas c to hionable obje ts collect , every one in his , or her , young days has listened with wonder to the supposed

a o f ea ca s are m ro r the s in their vitie , while there so e few who retain their predilection fo r them through " I o ut f a m a m s c c . li e , ke ore or less exten ive olle tions

r an s a an a Fewer p e still, however , p y y ttention to

f a d u fo r ha the anim al t hat ormed n b ilt the shell , it s

u a s m a never stood high in pop l r e ti tion indeed , u u a an o f a nless good to eat , it is su lly object ver s u o f a ion , and yet there is no gro p the invertebr te ,

a . or backboneless anim als, that better rep ys study

- a o f The Mollusca (soft bodied anim ls), which the

n an d Cuttlefishes Slugs a d Snails , the Oysters the , 2 THE LIFE OF THE MOLLUSCA

r f a are fam iliar examples, as now rest icted , orm well marked group (subkingdom or phylum) o f the animal kingdom . ff Owing to their plasticity, they di er very much

m al f among the selves in ext ern orm ; indeed, some of the more aberrant members are at first scarcely recog

l at all a f n iz ab e as molluscs ; nevertheless, part rom

c a f u the prote tive shell , which is leading eat re o f the

u a m a a f gro p , re rk ble uni ormity characterizes their a a a i a f a intern l org niz tion in ts m in e tures, especially in the you ng forms . “ E a a a a al xtern lly most possess . he d ventr ” a f n creeping org n , the oot ; a d a dorsal covering, “ ” e a an the mantl , which be rs d secretes the shell. This Shell forms a to the more Vital “ protection a an an n a org ns, d into it the imal ca gener lly with

f r draw o security from attack . The m antle does not usually reach far beyond the

- ut in shell m argin when the animal is extended, b some cases it curls round over the shell ( Plate II

an s C rwa s Fig . d even , a in the Cowry ( yp ), meet

P I . m r S c a on the top ( late L, Fig In the o e pe i l iz ed M ollusca there is a tendency to the reduction,

i a a a f n se even to d s ppe r nce, o the shell, a d in the there i s a corresponding liability fo r the shell to become more and more e nveloped permanently in the mantle as the animal becomes less and less able a f i s a a O a s e n ra . to use it pl ce retre t ( e f , p u a f The m scul r oot , which is generally an organ of GENER AL INTRODUCTORY 3

m a a u f ff loco otion , t kes v rio s orms in the di erent groups o f Mollusca ; the Univalves (Snails an d Whelks) creep along by its means ; the Bivalves employ it to b urrow with ; in the Cuttlefish it is “ ” drawn out into the arm s ; in other Mollusca it is

a f fin s s tr ns ormed into to swim with ; whilst in ome ,

s has a u an d has like the Oy ter , it ce sed to be sed ,

m u m M o f degenerated into a ere r di ent . ost the m uscles o f the body are concerned with the extension

r o f iff a o n d or ret action the d erent org ns f the body, a do not call fo r Sp ecial enum eration .

is m a m o f a a o f The shell inly co posed c rbon te lime,

m u c . f o f as ch as 95 per ent , in the orm calcite or

f a m x arragonite , being O ten present , with the d i ture “ o f a c u s u a co n ch o li n a hitino s bst nce , y little phosphate o f lime an d a trace o f carbon ate o f m ag

n esium are a . a lso present It origin tes in a. Shell

m an d uc gland , or pit , in the e bryo , the s cessive

a o f u i u P a I l yers which it is b lt p ( l te VII Figs . I an d 1 2) are form ed as the anim al grows by addition s

n d are s f to the margin , a depo ited in order rom the outerm ost to the inner one by a series o f Special

s m a o f m cell situated in the thickened rgin the antle .

u a c The o termost l yer , or ontains the greatest abundance o f chitine -lik e m aterial in its

an d o f at comp osition , is the work the cells the very

The e m e i e m i s which has een e en sivel t r p d r , b xt y m is a lie to his la e -sho ul be rese ve exclusivel fo p p d t y r, d r d y r the outer layer o f the ski n of the anim al itself. M LL A 4 THE LIFE OF THE O USC

fu edge o f the m antle . Its nction is to protect the u nderlying layers from the action o f acid in the

a o f a a . water, or from th t the we ther on l nd It varies greatly in appearance , being sometimes smooth

t an d a f an d Shiny, a others , rough co rse ; requently it

P . . 2 a . a f is fibrous ( late XXVI I I , Fig ) In m ny orms it readily rubs o ff in others it is firmly united to the true Shell beneath . The second , or principal

ua f a o f S layer, us lly orms the gre ter thickness the hell

a an d proper, or ostr cum , is secreted by cells f f a a ma arther rom the m ntle m rgin it y be coloured, an d Of a o f f is ten m de up prisms o calcite , as in

P im m f h a a , though it requently as porcell neous structure . The cells more remote from the mantle

t a f edge deposi the innermost l yer o the ostracum , thus

n thickening a d strengthening the shell . This layer ” a a o f r and f n creous l yer ) is a ragonite , requently f m a a or ed with overl pping pl tes , thus giving rise to

- - the iridescent appearance known as Mother o f Pearl . The remaining surface o f the mantle also secretes

S m a f r of helly tter on occasion , either o the purpose fu n rther strengthening the shell , o f repairing a injury f remote rom the edge , or o f filling up unoccupied

a P a . a sp ces ( l te VI I , Fig . and in most Mollusc this deposit differs in structure from that of the “ a " - other l yers In the pearl producing shells , how

Th “ e term hyp ostracum has been ap p lied to the Shelly l ayers Im m ediately un der the p o in ts o f attachm en t of the m uscles ha secu e th e anim al to the h l ot t t r s el , but they do n GENERAL INTRODUCTORY 5

and ever, such as the Top Shells (Tu rbinidae

' ae P a M eleu m uu an d a Trochid ), the e rl Oyster ( g ), m ny

' f a Mu m o Auodoutu a as reshw ter ssels ( U , , s well

autilus a f m f N , this l st or o Shelly secretion is not

ff a f m a u a an d di erenti ted ro the n creo s l yer , is very

f n d abundant . In the case o the Pearl Oyster a

“ f s a M f u a re hw ter ussels , oreign bodies introd ced cci

a o r i nt ent iOn all . m a o f dent lly y between the . ntle the

m n m ani al a d the shell beco e coated with pearl . In “ ” s wa s a an d a a a thi y bli ter pe rls , occ sion lly det ched

a are f m but u a o f c m m c p e rls , or ed ; the tr e pe rl o er e ,

as s a iu m . d will be hown l ter ( f , p is eveloped within the tissues o f the anim al . The successive additions along the growing edge o f the Shell generally leave ridges or m arks parallel “ a are as f . with it , th t known lines o growth The deposition o f shell does not go on continuou sly ;

an d a a a o f every now g in there comes period rest , an d these rest periods are frequently indicated by

u c f m the occ rren e o a stronger ridge or ark . The different details o f sculpturing on the surface o f the

e — a e — are all c sh ll stri e, ribs , sp ines , t a the produ ts o f corresponding irregularities on the m argin o f the m a an d s f s a he ntle, were, when fir t ormed , itu ted on t

. a uscs s a am growing edge Cert in moll , e peci lly ong a a fu o f the G stropod , rther possess the power dis

l in nd m s o f r h v g a re oving portion thei s ells , either ap p ear to differ in m icro sco p ic structure fro m the shell im l en ea h hem m ediate y b t t . ” 6 THE LIFE OF THE MOLLUSCA

as a from the exterior or from the interior, occ sion m ay requ i re . The lime fo r the shell being probably obtained by m f f a the anim al mainly fro its ood , it ollows , especi lly

f a in the case o f the vegetable eeders , th t where lime

a and is abu ndant in the soil or w ter , consequently in

m n the plant tissues, the shell tends to beco e ab or m ally thick and heavy ; while other mem bers o f the m c m a sa e Spe ies living where li e is sc rce , will have

a exceedingly thin Shells . The l tter condition is very observable in the larger Land Snails o f the Channel

s a I l nds , where , indeed , the living individuals will even resort to the shells o f their dead comrades to obtain the requisite supply . Isolated cases o f abnor mally thick shells are probably due to physiological

u a o f ua a ‘ a pec li rities the individ l , en bling it to bsorb m f lime ore easily than its ellows . I nternally the com m on trait in the Mollusca is the

o f o a a a reduction the c elum , or body c vity, to sp ce

a and a o f around the he rt , the concentr tion the prin cip al nerve centres into a ring or collar surrou nding the oesophagus .

o f u Bi ves All sections the gro p , except the yal , ” a a f a u a h ve distinctive eeding organ called the r d l , an d in their development almost always pass through “ a as i n ra wh t is known the veliger stage (see f , P 93)

a c w The he rt , whi h is ell developed , is entirely — a a a sa rteri l th t is to y, only receives the blood after

8 THE LIFE OF THE MOLLUSCA

f a extreme value in tracing relationships o the v rious

a m P a . , Fi . parts . Its princip l ele ents ( l te I I I g 3) comprise a series o f paired nerve centres or ganglia ; ” r c a a a a o o f these one pai , the erebr l g ngli , lying b ve

o ff a e the oesophagus , sends nerves to innerv t s the

an d a a of a head , eyes, the speci l org ns sense ; nother ’ a a a a pair, the ped l g ngli , is situ ted below the al a a oesophagus ; whilst the pleur g ngli , lying one

a al a a f on each side ju st bove the ped g ngli , orm the

a a a are third pair . These sever l g ngli united by

a f a nerve cords, so th t the whole orms ring or collar

Irio re round the throat . I n the primitive Mol lusca the two last nam ed are som ewhat removed back

a but from the other p ir, in the more specialized

re i and forms they a in proxim ty to it , the resultant

u m oesophageal ring is m ch ore concentrated . Four a f o f nerve cords run b ck rom either side the ring, two in connection with the pedal ganglia serving the f nd a a a oot , a two in connection with the pleur l g ngli

a. a are innervating the viscer These l st , which the

an d are more important , provided with minor nerve

are a a centres, united tow rds their termin tions, thus “ as forming a continuous loop , known the visceral ” loop .

Various sense organs are present. Many of these are a the u and are situ ted on integ ment, probably,

a a o f . E like the tent cles, org ns touch yes are found f m f in most orms, so etimes very per ect organs , as in the higher Cuttl efishes in Snails generally they are GENERAL I NTRODUCTORY 9

an d a a a o f less well developed, pl ced ne r the b se the “ r m o f a a a . horns, O on the sum it speci l p ir The

u ua Bivalves , being headless , have s lly no eyes ; but

a a and some possess them during their l rv l existence,

' they persist in the adult Mytilidae an d Ptem u Secondary visual organs are developed

nd u a in certai n forms, a more su lly occur in some part o f the margin o f the m antle or siphons (see

i n ra . ca o f u f , p In the se one or two moll scs eyes are developed over the back .

n f a a That molluscs ca hear is in erred, r ther th n “ ” o f a known, from the presence otocysts , sm ll cavities filled with fluid in which grains o f Shelly , r a t o i material float . These otocysts a e situ ted close

a a a an d u f the ped l g ngli , s pplied by nerves rom the

a a a P a . . ceph lic g ngli ( l te I II , Fig 3, From their discrim ination o f food some Mollusca a a a a o f as and a ppe r to be c p ble t ting , they cert inly f f can smell . The seat o the ol actory sense is believed

a and m a a to v ry, in so e to reside in tent cle, While in others it can be traced to a Special organ called the ” “ m osphradium , which in arine snails is Situated

and close to the gills, resembles them somewhat in appearance .

f all a o f M For procuring their ood cl sses the ollusca,

P c a are f s except the ele ypod , urni hed with one or a

a o f a a P a . . p ir horny m ndibles or j ws ( l te I I I , Figs 4 d a f a a an S a P a . the peci l eeding org n , the r dul ( l te I I I ,

Figs . 1 1 S A 10 THE LIFE OF THE M OLLU C

a The mandible is Single , and pl ced on the upper Pa a of side o f the mouth in the Limpets ( tellid e), one

' - ctzluceus La and the Sea Slugs (E gi res pun ), the nd

m a a P a . . Freshwater Snail s (Pul on t , l te I I I , Figs 5 ’ - D a an d and the Elephant s Tu sk Shells ( ent liidae). Two kinds o f P ond Snails (Li m urea an d Planorbis) have three m andibles an upper an d two side plates

m a of (Plate I I I . , Fig. The jority the other — gastropods fo r the carnivorous species are generally

— a a without them h ave two later l pl tes . Many of

re a m a a these a orn mented with ost el bor te patterns, and some have raised projections on them like a file

a . Fi . (Pl te I I I , g

a a a a f a The Ceph lopoda lso have p ir o m ndibles,

’ and m a Pa a a upper lower , rese bling rrot s be k, s ve

a P . th t the upper fits within the lower one ( late III , i F g . These mandibles are formed apparently of dense wt derm and chitine, strengthened in the case o f Ch o u

N autilus with carbonate o f lime . The radula is so importan t a f eature as to call for

" i car more detailed m ention . With ts supporting tilages and muscles it occupies the position in the r a mouth assumed by the tongue in the highe anim ls, and much resem bles that organ in general appearance.

a u a f s f of The r d l itsel , however, con ists o a series recurved f f teeth ormed o dense chitine, attached in v transverse rows to a membrane o f the same sub a st nce . In the Lim pets ( Docoglossa) the teeth GENERAL INTRODUCTORY I f Of a urther contain as much as 27 per cent . silic

a hydr te or Opal in their composition , while in the rest of the G astropoda the Chitine is hardened super

fi iall c a a m an d c y by deposits ont ining c lciu , iron,

a am u all f 2 6 phosphoric cid, o nting in rom 4 to per

s ff f m s cent . The Chiton di er ro thi second group in al one having ferric oxide as the m ost im portan t

m . u e is ineral constituent In s , not only the whole tongue- like m ass protruded an d worked with a

a a u a s ac a s an d licking ction , but the r d l move b kw rd

' forwards on its s urface over the cartilages like a

m a a chain saw . The nu ber o f teeth in e ch tr nsverse

a f m as a o f sea-S u s row v ries ro one , in cert in the l g

’

E oli s E l si a . an d s o f Chwtoderm u ( , y , etc ) specie , to

u a o f 200 00 as an d pw rds or 3 , in the Top Shells

' ' roc s Hulzotzs m their allies ( T hu , , When ore

a than one i s present the teeth generally vary in sh pe, but those on either side o f the centre correspond

m o f s a a f m each to each . The nu ber row lso v ries ro

a few m a a s m M u ca only to very ny, so th t in o e oll s , ,

L m a u a i s a as like the i pet , the r d l ne rly twice long '

as the anim al .

In all f , the teeth in ront tend to become worn

a a a use an d ac m f w y by const nt , to rep l e the resh

are ua f m at teeth contin lly being or ed the other end , which is kept in a special sac or pou ch under the

a u ae are a f u gullet . The longest r d l gener lly o nd in

m s L a f those ollusc , like the impet , th t eed on the

m s icroscopic plants growing on rock , the teeth in LL S 1 2 THE LIFE OF THE MO U CA such case being m ore qu ickly worn away by use . ff an d are The worn -o ut teeth usually fall o lost , but = in one tribe (Asco gl o ssa Elysio idea) they are received an d retained in a special sac. The total num ber o f teeth in the radula couse ff qu ently varies greatly in the di erent kinds . In som e species o f Chwtoderm u there is but a single

P a l II . . 16 tooth present , while the Whelk ( l te , Figs an d 1 ha a 2 0 a L m 7) s bout 5 , big i pet the Periwinkle the Comm on G arden Snail

' an d the big Grey Slug (Li m ux m uxzmus)

a a a m af a u a I n cert in inst nces they l ost b fle c lc l tion, as many as being com puted fo r Um bra

aulum .

Since each succeeding row o f teeth resembles its

a a a predecessor, longitudin l striped p ttern results when the teeth in the transverse rows vary in shape

an d u . a a a a colo r In e ch row there is gener lly centr l , ” rhachidian s a d or , tooth pre ent , fl nke on either side “ ” a a . a a m a o f by l ter ls These l ter ls y be one type, as in the Common G arden Snail an d its allies

Heli x m a ( ), or they y be divisible into two or three sets , when those nearest the central tooth are styled “ ” “ ” a a an d r m dmedi n the oute ones arginal , these two series bei n g generally divided by a conspicuous

m a a a b tooth , or jor l ter l . This is expressed y f m u a as I I I P a . . I 6 an d I or l e , ( l te I I I , Figs 7), 2 : I I I 2 P a I II . I an ( l te Fig 5), d when the m a a are u ao I co rgin l teeth very n merous, 5 5 GENERAL INTRODUCTORY 13

P a . . co co P a » ( l te I I I , Fig ( l te I I I ,

Fig . etc . The shapes o f the teeth are so constant in the several m olluscs that they assist not only in the

m a n o f fa s an d a ut few deter in tio milie gener , b , with

c a o f a . ex eptions, in th t species lso f s f are fu The orm o the teeth , rther, some index to

o f u u v the diet the animals , the p rely herbivoro s ha ing

ro ad- i a s a short, b po nted teeth , the c rnivorous h rp _ f pointed teeth , which in those eeding on living

im r a an als a e barbed to ret in their prey, while in the

r a u f Cones the teeth a e not only b rbed , b t per orated an d connected with poison glands .

M u are far f In habit the oll sca rom active , only som e o f the Cuttlefishes being capable o f sp asm odic ” a so uc so a t erm u r pid motion , m h th t the sl ggish ,

f m m m . borrowed ro the , best describes the The exact relationship o f the Mollusca is difficult

u to determine , tho gh they belong to the sam e

O a m a as a a division f the ni l kingdom the Ch etop od ,

a f a B a an d B ac a bu Gephyre , Roti er , ryozo , r hiopod ; t on the whole it is considered that the m ost archaic m u s m a s oll scs, the Chiton , co e ne re t to the free

’ P as au Sea- M u A hro zte olychetes , such the g dy o se ( p d ), so common on o ur coasts . CHAPTE R I I

C L AS S I FI CAT IO N

HE Mollusca are divisible into five principal groups or classes

S I . : CLA S The AMPH I NEU RA , of which the

- — Chitons (Coat o f Mail Shells) are the type .

a u In these the body is more or less elong te , witho t

a a f f a u fa . distinct he d, the oot orming the ventr l s r ce The extremities o f the alim entary canal lie at either

o f an an wa a a end the body, d do not in y y pproxim te

a u a are ua each other , while the v rio s org ns sit te in

o f a th pairs on either side the central axis , so th t e

a o f an d a a two h lves the body. correspond , the nim l i s symmetrical .

a POLYPLA This Cl ss is divided into two orders,

COP HORA n P AC PH a d A L O ORA.

- — . P OLYRLACOFHORA a o i Ma Order I , the Co t il

Shell ‘ r — s o P a . . 1 a , Chitons ( l te IX , Figs 3 ; Radul

P a . . 1 1 r l te I I I , Fig ) a e readily distinguished by being alone am ongst the Mollusca in possessing a " S o f m a a a. helly covering ny pieces , c lled , the loric I 4

16 THE LIFE OF THE MOLLUSCA

a a o f Ventral side o f the body . The r dul is the

- many toothed order or wanting .

- E RMATINA e e Sub Order 2 : C HE TO D , repr s nted by

e P . a single genu s Cheetod rma ( late I X , Fig . in which the bo dy is ex tremely long and cylindrical ; f a the oot is w nting , its position being merely indi cat ed by a groove ; whilst the radula is represented

by a single too th.

CLASS IL : The GASTR OPODA ( Plate

fied by the Snail and Whelk .

a I n these there is distinct head, furnished with

a o f a one or two p irs contr ctile sense organs, the “ ” ” a tent cles , or horns , the form o f which varies

greatly in different grou ps . The two eyes are situated on the tentacles (the hinder pair when four

are an are present), d generally carried on tubercles

a a ne r the b se, but they sometimes appear halfway

l C a and up , whi e in the ommon Sn il his kindred they are a f of , as well known , borne lo t on the summits “ the horns . f f a d The ventral oot orms creeping isc, and sur mounting it the visceral organs Within the covering

a r as a w e m ntle a e borne t ist d hump, generally f covered by a shell ormed in a single piece . This

a a shell is tt ched to the body by a powerful muscle,

a which serves to withdr w the animal into its house. The torsion o f the bo dy is brought about by a — a . Fi . 1 A D . F as double process (Pl te I V , g , ) irstly, CLASSIFICATION 17

l fi h a a f f ar in the Cutt e s es, the l tter h l o the aliment y canal is bent underneath the body till its termination a i p p roxim ates the m outh . Then the visceral mass s

s u a a a m a twi ted ro nd l ter lly, so th t the ter in l portion o f m a ca a n the ali ent ry n l , with the two gills a d other

a a f ar u p ired org ns on either side o it , e bro ght round by the right side till they lie nearly over the head , an d the original left gill an d accom panying organs

m o s - a beco e in p ition the right h nd ones , while the visceral nerve loop is twisted into a figu re o f 8.

N x a f n e t , the origin l le t (now right) gill a d it s acco m panying organs tend to wither an d eventu ally dis

s m cas s ap pear . In o e e the secondary twist takes

ac s c u f pl e in the rever e dire tion , or ro nd by the le t

a f - a a m a u s an d side , when le t h nded ni l res lt , the

a etc. are u s origin lly right gills , , s ppres ed.

wa a m a m a m a In this y the ni l beco es sym etric l, organs on one side o f the body not being matched

fu u by corresponding ones on the other . A rther res lt o f a a is a w c the second ry , rot ry twist th t the shell , hi h

’ was c f a a a a beginning to oil orw rds over the nim l s he d ,

a a as N auti lus u or exog stric lly, it does in , is sw ng

a s a a a round so th t it coil b ckw rds , or endog strically . The shell secreted by the m antle covering this

um o f i twisted visceral h p, course, reflects t s form

u in every respect . E ssentially the res ltant shell is

a s w . m u longer or horter hollo cone In so e , s ch as

a u L a m u the d lt imp et , it is si ple cone , b t in by far

a um an a c the gre ter n ber it is elong ted one , co iled 1 8 THE LIFE OF THE MOLLUSCA

ac c f m a round an d round , e h oil or ing whorl, the ” a V . . 1 l ast being the body whorl (Pl te , Figs to

' m a a flat a Thi s coil y be one , but most G stropods have the visceral dom e an d shell twisted dextrally

i sa a that s to y, when the shell is pl ced with the

' u m s an d a ex d irected a a m outh pper o t , the p w y from

u a the observer , the mo th lies to the right h nd o f the

r axis o f the shell . Some a e wound in the opposite direction and are sinistral . Reversed varieties of a a s an d a nim l shells norm lly dextral , or normally s a are f as a inistr l , o ten met with , well s species in which the coiling o f the anim al and shell is indiffer ently dextral or sinistral in the individu als composing

. are a t it There , moreover, G s ropods whose shells coiled in one direction enclose anim als whose organ iz at io n i s that usually associated with Shells having m the opposite twist . Thus a ong the Am p ullaridae there are an imals with dextral organization occupying

L uul t s sinistral Shells ( s e ), while in the Planorbidae the comm on Flat- coiled Water Sn ail (P lanorbis) is an exam ple o f a normally sinistral animal in an appar

u ha ently dextral shell . This is bro ght about by w t ” as h erst ro h an d m a a is known yp p y, y be illustr ted

a a f flat an by t king per ectly , coiled shell d placing it with the m outh downwards an d directed away from

O P a IV. i . A a the bserver ( l te , F g 3 , ) then in dextr lly

a a a m org nized molluscs th t ssu e a Spiral growth, the sp ire wou ld normally be exserted towards the right

P a . . B C m a l be ( l te IV , Fig 3 , , ), but y exceptional y CLASSIFICATION 1 9

x f P . a S a . e serted tow rds the le t ide ( l te IV , Fig 3 , ’ B ca , In the first se the shell will be dextral , in the latter sinistral . With sinistral animals these

s r condition a e just reversed .

’ ' ’ c a f m s Odostom zu Turbom llu Tom utzuu In ert in or ( , , ,

. s a af x etc ) the young hell is sinistr l , ter which de tral

u u an d m growth s ddenly ens es , the co pleted shell is “ x a P a . . m de tr l ( l te IV , Fig The ter hetero st ro h has a c p y been pplied to this ondition . ” a u a o f is m m The xis , or col mell , the shell so eti es “ ” u hollow , or mbilicated (the hollow itself being

ca P a . i um cus F . an . lled the bili ( l te VI I , g 9 ; d VI ,

. s m s are an Fig 3) o etime the whorls closely coiled, d f a a O su P a . . solid pill r shell re lts ( l te VI , Fig In

' u N utzcu um c i s ut m the gen s the bili us open , b in any o f the sp ecies the cavity is m ore or less filled by a ”

S as a u P a . . helly deposit known c ll s ( l te VI , Fig 3 , — “ ” A E ). The apex or extreme top o f the shell generally differs in m arkings an d other features from

an d ff a c a ac s . the rest , o ers import nt h r ter This “ ” ” u c f m nucle s, or protocon h , is the p ortion or ed

c a a m in the egg, hen e it is lso known s the e bryonic ” shell . The spiral channel formed by the j unction o f the “ a whorls is termed the suture . A spir l line traced along the whorls midway between the sutures would ” ” a . m a m rk the periphery The outh , or perture , has m m u a c u a m a so eti es q ite irc l r rgin (peristome), “ ” when it is said to be entire or continuous ; S 20 THE LIFE OF THE M OLLU CA

” u more often it is interr pted , the side next the colu mella being bou nded by the wall of the body as whorl only , when the exterior portion is known ” um an d the outer lip or labr , the other side as “ ” ” u m a a . the inner, col ell lip , or l bium There is frequently a notch in the m argin o f the aperture near the junction o f the outer lip with the body

n a a whorl , a d nother where it joins the nterior end o f the columella ; these are respectively termed the ” n a a a n d posterior a d nterior c n l, a give passage

‘ to t he siphons o f the anim al . (All these terms are illustrated on Plate VI This group has been called a an d n siphonostom tous, those without a y notch ” u holostomato s . a f Pleurotomurl u In some rhipidogloss te orms ( , the

lero hou E m ur iuulu . and fossil Be p , g , etc ) the toxo glossate Pleurotom a there is a slit near the periphery o f the labrum that gives passage to the anal fold Or — — Hull otls . siphon . In others , etc the slit gives

o f f a place to a series per or tions (Plate VII., — 1 8. a i n ra . . an d Figs. See lso f , pp 94

an - S The labrum is thin d harp in most shells, and in some adult forms ; but m ore frequently it is u a either thickened, or curved o tw rds (reflected), or ” a curled inw rds (inflected), or expanded or fringed .

n with spines . Whe these thickenings or expanswns a occur periodic lly during the growt h o f the shell,

f a m they orm conspicuous tr nsverse arkings on the . whorl termed varices . The exterior of the shell CLASSIFICATION 2 1 is also more frequently than not ornamented with either sp iral lines or ridges running in the direction o f growth , or with trans verse markings coinciding

the f P V . with lines o growth or with both ( late ,

Fig . 1 1 The external spines that com e in the way o f the growth o f the shell as whorl is added to whorl are

m wa n d m a m a . dissolved in so e y, a re oved by the ni l In som e cases also the internal walls o f the whorls and the columella are sim ilarly rem oved to m ake

' m m fo r u N em tu ore roo the growing creat re ,

'

heodo s . 1 n d I T xt C m u ou s P a . 2 a , yp , C u "l te VI I , Figs ' l Aum cu u,

a a m a u On the other h nd, when the ni l in the co rse o f av a s a u s growth le es p ce in the pper whorls , thi is

P . either filled up with a Shelly deposit ( late XXXI I ,

u ff m f a Fig . or c t o by the for ation o a w ll or

u a P a . . s.m . n d sept m cross the whorl ( l te VI , Fig 2 , , a

Verm etu m f u in s, A si ilar partition is o nd when the apex o f the Spire becomes worn through

a a a M u or broken by ccident , or tt cked by boring oll scs

P a . . i s off as a u a ( l te VI I , Fig or broken reg l r

’

f e. successive phase o the anim al s existence ( g . in

um i na deoollutu Cceoum "Plate VI I Fig . R

P a VII . . "l te , Fig f P Many o the G astropods , like the eriwinkle ,

o f close the mouth the shell , on retiring into it , with

On e an d o n l o n e in s an ce o f his in a helico i has een , y , t t d b — ecor e Via in a s ecies of Gl tostom a . r d d , p yp 2 2 THE LIFE OF THE M OLLUSCA

- a trap door ( Plate VI I I . , Fig . the operculum ' s a a a and when extended , thi lies on the nim l s b ck, in m any cases form s a sort o f pillion on which the

1 an d P a . . I . shell rests (Plate I I ., Fig . , l te V I II , Fig )

a It consists o f a horny l yer, sometimes strengthened

a ff by the addition o f Shelly m tter, which di ers in structure from that o f the shell itself. Its inner side is m arked by the scar o f the muscle which is a a d of tt ched to it , while outsi e it exhibits lines

. um a f o f growth The opercul , v rious orms which — are s P . . 1 hown on late VI I I , Figs 4 3 , grows by a a a o f dditions m de to the origin l point beginning, “ ” all u a the nucleus , either ro nd, concentric lly ; or

a m a on one side, so th t the nucleus re ains t the end or at one side or the growth m ay result in a spiral .

a a This spir l is sinistral in dextral , dextral in sinistr l

N a all r fu shells . e rly the Gastropoda a e rnished with an operculum in the young stage within the

an egg, d though some discard it on hatching out, th e greater number retain it throughout life . Many o f the spiral an d concentric forms fit the m outh of

a a the shell ccur tely, others only partly close the a u m m pert re , in yet others it beco es rudi entary, while

a a f rom bus and in cert in speci lized orms , such as St a its llies, it is converted in to a sort o f claw at the

o f o n a f end the el g ted oot , an d is used to assist the a m a P a ni l in progression ( l te VI I I . , Fig . A m ore peculiar m eans fo r blocking the entrance of the shell when the animal retires into it is possessed

2 4 THE LIFE OF THE M OLLUSCA

SPIDOBRANCHIA a i Order I . A , h ving the g ll

- filam ents flattened o ut into leaf like expans ions . — - A P a . . Sub Order I DOCOG LOS S ( l te IX , Figs 7 9 ; L Radu la, Plate I I I . , Fig . comprising the impet

fam ily .

- HIPIDOG OSSA P a Su b Order 2 : R L ( l te IX Figs . — 1 0 a u a P a . . m 2 4 ; R d l , l te I I I , Fig co prising the

m s a ae K L Fis urel Or er (H liotid ), eyhole impets ( s

lidae . m a ), etc , in which the older embers still ret in the f right (originally le t) gill , while the more special ized

a f a h ve only one, the le t (origin lly right) gill .

. : PECTI IBRANCH Order I I N IA, having elongated m gill fila ents . Sub- Order I : TE NIOG LOSSA (Plate which

u a a o f su - n incl des the gre ter p rt the b class, a d in which the radula formula is generally 2 1 I 1 2

P a . . ( l te I I I , Fig

- E Sub Order 2 : ST NOGLOSSA. I Tribe 1 : RHACH GLOSSA (Plate XL), including

s Do - an d n the Whelk , g Whelks , their kind, a d f m o f I a a a . h ving a radul or ul ( Plate I II ,

Fig . although in higher members o f the tribe

1 P a . this is reduced to ( l te I I I . , Fig

2 : O OG OSSA P . 1 o f Tribe T X L ( late XI I ., Figs which the Cones and Auger Shells (Terebm ) are the

- am 0 1 best known ex ples . The radula formula is 1

P a . ( l te I II , Fig . or exceptionally 1 I 1 . Sub-Class 2 The E UTHYNE URA fall into two orders an d four sub-orders CLASSIFICATION

I. : PI TH ANCHIA a u Order O S OBR , so c lled beca se the

heart is in front o f the gills .

- Su 1 : E CTIBRANCHIA P a . s b Order T ( l te XI I , Fig .

6 r or those h aving shells, which a e mostly f a a and f c a r gile or rudiment ry, o ten con e led in the

- folds o f the m antle . To this belong the Sea H ares

ae Bu a etc. (Aplysiid ), the ll s ,

S u - : N UDIBRANCHIA P a b . . Order 2 ( l te XI I , Figs

0 s - Sea- are x 2 or the hell less Slugs , e ternally

m m ca a a u u sy etri l nim ls , witho t tr e gills, respiration

ff c c a s a being e e ted by se ond ry gill , or by the gener l su fa a s m cas a r ce, ided in o e es by the cer ta, which are appendages o f the dorsal integum ents .

. : P U MONATA m a o f a Order II L , or the jority l nd an d f s a c u has re hw ter shells , in whi h the tr e gill

a a an d f a u dis ppe red , its unction is t ken p by the wall o f the mantle cavity .

- 1 BASOMMATOPHORA P a . Sub Order ( l te XI I I ,

1 a at as f Figs . or those h ving eyes the b es o the

a m a f s a u m a and tent cles , e br ces the re hw ter p l on tes a few land shells .

- u : TY OM MATOPHORA P a . S b Order 2 S L ( l te XI I I , — 1 1 and P a a u a P a . Figs . 35 , l te XIV R d l , l te I I I ,

n s a Figs . 2 1 a d or those having the eye t the “ ” o f a a all end the horns, t kes in ne rly the land shells .

: P P D LEN CLASS II I . The SCA HO O A , or SO O

1 and o f CO NCHA ( Plate XV . , Figs . which the 2 6 THE LIFE OF THE M OLLUSCA

' ' - f Elephant s Tusk Shell (D eutulzum ) is the type , orm a s ingle sm all group by themselves . a u a The anim al is symm etrical , with r diment ry

a an d a a f u fo r he d , long cylindric l oot sed burrowing in the m ud in which these creatures live .

o f a are a The borders the m ntle united bene th, f a t orming tube , open a both ends , enclosing the

s o f an d a u a re t the body , enc sed in the tub l r Shell, which is likewise open at both ends , there being no approxim ation o f the two ends o f the alimentary canal . There is generally a notch in the margin of the shell at the smaller end (or posterior opening)

a . chizo on the ventr l or convex side In one genus, S

' deutalzum are a an d , there , besides , in line with close

o f . to this notch , a series openings Sometimes the shell is finely striated lengthwise .

ASS P E E YP DA LAMELLI CL IV . The L C O , or B N RA CH IA (Plate XV Figs . 3 commonly

as B o f Mu . known ivalves , which the Oyster, ssel , etc ,

re f rudim en a amiliar examples . In these the head is

a CE PHA A Cu t ry , hence they were called A L by vier ; while, because a head is present in the embryo but does not develop , Lankester proposed to term LIP E P AL them OC H A. The characteristic radula is, o f u - xe co rse , wanting in this group . The stone a

S a f u ua n as h ped oot is s lly well developed, a d serves

a u an d a . b rrowing , r rely, as a creeping organ The symmetrically disposed organs o f the body CLASSIFICATION 27

an d f o f are enclosed between the two , right le t , lobes

m u are c the antle , which in their t rn overed by the

fe a a a . a w two Shelly p l tes , or v lves In inst nces the

a and m antle is extended an d reflected over the v lves , i odoutu partly (Galeo m m idae) or com pletely (Eph pp ,

m . etc .) envelops the The m antle lobes are attached along the back an d extend o ut to the m argins o f the valves . In the m ore prim itive form s the mantle m argins are quite

m an d f m f a si ple , open ro the ront round the ventr l edge to the back ; but m any different modifications take place in the higher form s . Instead Of the m a m m a f c rgins being si ple , there y be olds , thi ken

u a c ac P a . . ings , prot ber n es, tent les ( l te XV , Fig

a a and v P a . . v rious gl nds , e en eyes ( l te XV , Fig

N r re m a a a f m o a the rgins lw ys ree indeed , in extre e

cases they are united nearly the whole way round . — are a a P a . . A F There v rious st ges ( l te IV , Fig 4 , )

c as A re koning the open one the first ( ), then in the

B s a f a m ll second ( ), in te d o the w ter being ad itted a

wa u f m ar the y ro nd, the edges o the antle e kep t closely applied to each other except where the foot

u s an d at s at bin der protr de two point the end , one

o f a m f a which serves to d it the resh w ter to the gills , “ ” an d a a a is c lled the inh lent perture , whilst the

a f u a a n other llows the o led w ter to esc pe , a d is ” term ed the exhalent aperture . In the next stage

C o f m a are u a ( ), the edges the ntle nited perm nently at the point between these two openings an d in the SC 2 8 THE LIFE OF THE M OLLU A

f u s a D at a a o rth t ge ( ), , second point below the inh lent

f a E a o f apertu re . In the fi th st ge ( ), the m rgins these

apertu res have grown o ut into tubes

an d a o f Plate XV . , Fig . the rem ining p ortions the

s a u all u m antle margin h ve nited ro nd , except where i F the foot is protruded . F nally ( ), the two siphons

x P . . becom e u nited e ternally ( late XV , Fig In the se cases there i s frequently a fou rth s m all aperture

f a a . le t in the ventr l m rgin The siphons , the ends o f

r f f an which a e o ten ringed , c be wholly or partly

withdrawn .

ills a a The g lie underne th the m ntle , one on either

P a . . a side ( l te XV , Fig 3 , portion sh ded with straight

an d . 8 by s a a lines Fig , ), in the p ce between the l tter

m a an d the body o f the ani al . These org ns vary progressively from a very simple structure to a very

a an d has complic ted one, since their structure been f m ade the basis o f the classification O the group, a

brief description o f it is necessary . In the more prim itive Bivalves the gill is o f the asp ido branch

auto . P a . . a type ( , p 7 , l te IV , Fig 5 , ) ; but in the

are filibran ch fila higher Pelecypods they , only the

f a f ments o f each o the two rows , inste d O remaining

a a a an a a sep r te , h ve rr ngement whereby they inter

and f a a lock orm continuous membr ne , like the web

o f f a eather . The mechanism by which this is

u a u m bro ght bo t is extremely si ple . At regular intervals on either side o f each filament are little patches o f stiff hairs which interlock with the corre CL ASSIFICATION 29

m sp o n din g ones on the two neighbouring fila ents , just as two brushes m ay be made to do ; these “ ” are known as the ciliated junctions ( Plate IV

. E . M m m a am a Fig 5 , ) oreover , the two e br nes , l ell e , m e f a but thus arising do not si ply d pend rom the xis , their edges are folded u pwards so as to keep them

u am a within the m argin o f the shell . The o ter l ell is f u a s n d a ds so a olded o tw rd , a the inner inw r , th t

f m a s c P a . . B . they or W in e tion ( l te IV , Fig 5 , ) A further com plication o f structure ensues when ” u a am a u are f m j nctions , c lled interl ell r j nctions , or ed between the dependent p art Of each filam ent an d its

m c s a reflected portion . In a ore advan ed t ge still both the ciliated an d interlam ellar j unctions becom e s c s SO a u u s s olid onnection , th t the whole str ct re pre ent a - a a a o f sp onge like ppe r nce , while the reflected ends

am s u o f m the fil ent , niting with the walls the antle

n f a d su v a a C a P a . oot , bdi ide the p lli l h mber ( l te IV ,

. C . fu m Fig 5 , ) One rther develop ent there is , in which the gills have become converted into a sort

o f a - a s a m p rty w ll , eparating the p llial cha ber into a

a an d P . . . dors l ventral portion ( late IV , Fig 5 , D) At certain points all over the gill filaments there

are f ac a power ul cilia, which by their tion keep brisk current o f water flowing over the gills in a constant

stream from behind forwards . This not only insures

a f f u c s m c resh supply o oxygen , b t onvey the i ro organisms o n which the anim al feeds towards the

mouth . L 30 THE LIFE OF THE M OL USCA

The muscu lar foot is a prominent feature in most m a f Bivalves , lying in the iddle line tow rds the ront — P a . . 6 8 . a Of the body ( l te XV , Figs 3 , , f ) Tow rds the back o f it is situated the gland fo r spinning the horny threads by which m any Bivalves anchor them

etc. m M and selves to stones, The Co mon ussel the

re f a a an d Zebra Mu ssel a amili r ex mples , the bunch “ ” f as u P a X . o threads is known the byss s ( l te V , h f . b . a m a a as o Fig 9, ) The ni l gener lly the power rejecting its byssus at any time and spinning a fresh one . The m outh is Situated a little behind and beneath

f u m u a the ront add ctor uscle ; it is n rmed , neither

a jaw nor radula being present . It is fl nked on either “ a a o f a u a a a side by p ir twin , tri ng l r lobes, the l bi l ”

a P a . . t re a p lps ( l te XV , Fig 3 , ), which a in line

n f f l fu with , a d in ront o , the gi ls . Their nction is a a an d a f pp rently to collect , possibly to t ste , the ood before it passes into the mouth .

Ea a o f a u a ch v lve the shell is hollow , irreg l r, ” a a o f m a sh llow cone , the pex which , ter ed the be k, ” u m at a and or bo , is the point which growth beg n , ” fa u : is , in ct , the yo ng shell , or prodissoconch it generally differs in shape an d markings from the later growth . The um bo is usually curved more or less to one

P a . . 1 an d 2 u and a side ( l te XVI , Figs , ), gener lly

a a a points tow rds the he d, or nterior end, when the ” s sa ro so r hell is id to be p gy e, in contradistinction

32 THE LIFE OF THE MOLLUSCA

They are someti m es n umerou s an d all alike (Taxo

a m a dont), especi lly in the ore primitive Biv lves

lu cu . P a . . 1 6 N ucu ; A r , etc ( l te XVI I , Figs , 3 , ,

M a are a ore usu lly they divisible into central, more ” a o f a a or less tr nsverse , group c rdin l teeth, flanked on either side by others running with the shell “ a a al e . m rgin , or l ter te th (Teleodont) This shell margin bearing the ligament and teeth is known as ” an d the hinge line, is sometimes extended inwards

f a o f a f so as to orm sort pl t orm, the hinge plate

I . F . 1 an (Plate XV , igs d The number of teeth

al ff and a in the two v ves di ers , occ sionally, as in

hum u an a a C , individu l will h ve the normal dentition

of a a the two v lves reversed , condition apparently corresponding as near as such m ay be to sinistrosity

in the G astropod . The teeth become exceptionally strong in shells that live in situations exposing them a n an d a a to str in , a d dwindle dis ppe r in such as

dwell in protected localities . The possibility o f the valves being lateral ly dis placed is further guarded against in very many by tooth -like crenulations o f the ventral margins o f the

a a as C v lves th t interlock, in the Scallops, ockles,

a X i . 8 a . Fi . etc. (Pl te V., F g Pl te XVI II , g The Shelly tubes secreted by the Ship-worm

Teredo a X . . ustroch u l X X ( , Pl te X , Fig G wu (P ate I

. a Brechi tes X Fig the W terpot Sh ell ( , Plate X

Fig . an d so me others to line their burrows are r i r p oduced, it s t ue, by extensions o f the mantle or CLASSIFICATION 33

a u fa f a a but are f cuticul r s r ce o the nim l , distinct rom

a T re and Gastrochceuu the re l shells , which in the c do are Breohites within the tube and free, while in they are built into its wall . The points o f attachment o f the adductor muscles to the shell are m arked by well-defined scars — P a . . 1 o . u. an d a . ( l te XVI , Figs 3 , p ) Close to the

a u c o f fo r posterior dd ctor s ar, that the muscle with — f a f . . 1 m . dr wing the oot (Plate XVI , Figs 3 , p ) is ound , and m inor scars occur nearer the umbones o f the valves to which other small muscles are attached .

f soar at a Running rom one adductor to the other, s f m a o f hort distance rom the ventral rgin the shell , ” a a a a P a is sh llow groove , the p lli l line ( l te XVI — . 1 l c a a m o f Figs 3 , p ), whi h marks the tt ch ent the m antle edge . In those molluscs that have large

a m h a fo r retr ctile sip hons , roo as to be m de these, and a a f f a c u the p lli l line , instead o orming ontin ous

u a s f c rve , t ke , shortly be ore it reaches the posterior

a a a sc r , sh rp bend backwards towards the centre o f

a f m u as the v lve , or ing a bay or sin s , known the “ ” a a s us Fi . f p lli l in (Plate XVI . , g The size o this sinus naturally corresponds to that o f the siphons .

B a M f In some iv lves, such as the Common ussel o

o f the seashore , the posterior portion the body is more developed than the anterior . This develop ment tends to bring the two adductor muscles and

n t the hinge into a line , a d in propor ion to render 3 34 THE LIFE OF THE M OLLUSCA

the anterior adductor su perfluous, with the result that it tends proportionately to dwindle and dis

a do appear , leaving the enl rged posterior muscle to

h f a O and a t e work o both , s in the yster Sc llop — P a . . A D . B a ( l te XVI , Fig 3 , ) iv lves with two ” adductor m uscles are termed Dimyaria ; and if the ” f ar a latter are o equal size , e s id to be Isomyarian ;

if ua a a or, uneq l , Heteromy ri n whilst those ” having only one are called Monomyaria.

P r u The elecypoda a e s bdivided , according to the

u o f f struct re the gills , into our orders

I . : P R TOBRA CH . . Order O N IA (Plate XVI I , Figs 1

- f f a in which the gill filam ent s take the orm o fl ttened,

- af As i o branch P a . . le like expansions ( p d , l te IV , Fig

A . Nu N uoula an . 5 , ) To this order the t Shells ( ) d their a an d a a llies belong , probably lso the e rliest known

B f s u a a ivalves, orm now q ite extinct , th t h ve been ” few termed Pale oconcha. With exceptions they have a taxodont hinge.

: I IBR A CHIA a . . Order I I . F L N (Pl te XVI I , Figs 5

a - fil am ent o f having long, p rallel gill s, the ends which are f u f m a and olded p , or ing W in section , locked together by ciliated an d s ometimes interlamellar

P a . . . junctions ( l te IV , Fig 5 , B) To this order the

M l an d P . Ark Shells , usse s , ectens belong

: E . Order I II . E U LAM LLIBRANC HIA (Plates XVIII ,

. an d . . 1 l a XIX , XX , Figs in which the e ong ted

am are f u and fil ents yet longer, more olded p , per m an en tly united at intervals till they form a com CLASSIFICATION 35

let e s P a . . C . p pongy network ( l te IV , Fig 5 , ) The

f u u Oysters , reshwater M ssels , Cockles, Ven s Shells ,

- M a and are a o f s . y s, Ship worms ex mples thi order

T A CHIA P a . s . Order IV . : SE P IBR N ( l te XX , Fig 20 in which the gill -filam en t s are com pletely fused an d transform ed into a continuous muscular

s u a m o f ept m , with several perforations to d it the f w a o f P a . . D . e circul tion the water ( l te IV , Fig 5 , ) A

- f r iidae Ce o co nchidae an d deep water orms ( Po o m y , t , Cu spidariidae) constitute this order.

L D P a XXL CLASS V. : The CEPHA O PO A ( l te ),

o f c N us Cuttlefishes and whi h the autil , the ,

r m u m o f m Octop ods a e exa ples , incl des so e the ost

f M u a as as highly organized o the oll sc , well the

a fo r c ai Of Cu tlefishe calcu l rgest, ert n the t s, it is

a 0 f . l ted, exceed 5 eet in length

a a are m a a a s The Cep h lop od sy metric l nim l , the

a o f c u two h lves the body corresponding in stru t re .

a o f c a la The he d, on either side whi h there is rge

an d - is s n well developed eye, more or les distinct , a d

u b f has s a is s rrounded y the oot , which , so to p e k,

P a XXL . I . N grown round it ( l te , Fig ) In the autilus

m s o f f are the argin the oot divided into lobes, each bearing a group o f tentacles furnished with suctorial

are a S c a ridges, that retr ctile within pe i l sheaths

P L . u ( late XX , Fig In the other gro p s the pedal appendages take the form o f four or five p airs o f “ m s a f elongate ar s , the e rms being urnished with

rows o f suckers or o f hooks . SC 36 THE L IFE OF THE MOLLU A

' f e arm s and The m outh lies in the centre o thes , i s furnished with a pair o f powerful chitinous j aws ’

k . . that resem ble a parrot s bea ( Plate I I I , Fig a while the radula, though proportion tely small, is

P . . well developed ( late I I I , Fig The symmetrical body is surrounded by the bell

a m c a a shaped m ntle , covered in so e ses by shell, while those without an external shell frequently have lateral fins . On the ventral side a cavity is left between the

a an d a XXL . m ntle the body (Pl te , Fig 3 , In

a a are l an this m ntle c vity the gills (g) p aced, d into it the termination o f the reflexed alimentary

as as - t i canal opens , well the ink sac ( ) , with wh ch

o f m ost members the class are provided . Just at the mouth Of the mantle cavity two lobes o f a f f and the skin bove the oot , sometimes ree some “ ” a a f a f times united t their m rgins , orm unnel or “ ” a siphon (f ). Through this siphon the w ter is discharged from the mantle cavity ; quietly during f ordinary respiration , or with great orce when the creature propels itself backwards through the sea by a means o f the eject ed stream . Through the s me orifice the animal can at will eject the inky fluid f - ac h a rom the ink s , with which it clouds t e w ter on emergency when seeking to escape its foes . This power is possessed by all the living Cephalopoda

'

a N autilus Cl rroteuthzs n ol us. s ve , , a d two species o f P yp -sac was nd An ink present in the fossil Belemnites, a CLASSIFICATION 37 there is a picture in the possession o f the Geological Society of Lo ndon representing the fossil head o f a reptile (Ichthyosaurus) executed with the fossil sepia from a Belemnite preserved in the same strata. The gills of the Cephalopoda are asp idobranch in

n f u m : a type, a d either o r or two in nu ber the cl ss is consequently divided into Tetrabranchia and

Dibranchia. m f r Among the Cephalopoda we eet , o the first M o f time in the ollusca, with internal structures

a — m a — are gre t import na ely, c rtilages which espe ciall i i y developed n the head . In N aut lus there is

n H- a u a a sh ped cartilage, which s pports the ventr l

of Of a portion the nerve centres, two its br nches

a o f Di ran extending to the b se f the unnel . In the b chia a cartilage completely invests the central nervous

o a D ff system , the esoph gus passing through it . i erent Cephalopoda have additional cartilaginous pieces in

a o f u a other p rts the body, s ch as the b ses o f the fins and a a rms, t the base o f the n eck (when the mantle f a is not used to the he d), at the internal ext remities o f a o f n the retr ctor muscles the head and funnel, a d

a al even in the two br nchi lamellae .

a fu The shell, s seen in its llest (external) develop

Na an d f a ment in the utilus its ossil rel tions, as well as A m a f in the m onites, resembles th t o the G astro a f pod in consist ing o a single conical tube . In the earliest kinds of Nautilus (Orthoceras) the shell is a quite str ight, in some others it is curved ; but in 38 THE LIFE OF THE MOLLUSCA the m ajority o f N autiloids and Ammonites it is more

i i ll an d, a or less coiled d sco da y, gener lly the coil is in ’ a f a c a a a orw rd dire tion over the nim l s b ck, or exo ” a . f are g stric A ew, however, coiled in the reverse ” r a direction , or a e endog stric ; while in some cases

u a the coil is prod ced into helicoid, or even a turrion lated spire . I n yet other instances the shell m ay be a n coiled in the young st te , a d become m ore or less

Sca hi tes Cri oceras Hami tes . uncoiled ( p , , , etc ) or even straight (Baculi tes) in the adult (Plate

f a o f a The striking e ture the Ceph lopod shell , how P ever, lies in its internal structure ( late L). As the a a f nim l grows , it builds on to the open end o the

to a a a u shell obt in incre sed ccommodation , j st as the Gastropod does ; but since it g rows in girth m ore than

ha a a in length , it s, in order to obt in the requisite sp ce, to shift bodily forward in its shell . This takes place gradually by the forward growth o f the shell muscles on either side an d the intervening pallial attach m ents till an unoccupied Space is thus

f a o ff a S le t behind , which is then p rtitioned by helly

u w o f wall sept m in this ay the series chambers, so fa a f u re f mili r in sections o the Na tilus shell , a ormed, each m arking the com pletion o f a period o f growth.

a are f The sept , however, not entire , a per oration in each is connected with that in its neighbour by a

a a a a pipe, in p rt c lc reous, in p rt chitinous, the whole forming a continuous tube which passes from the

u e a o t rmost ch mber, or that occupied by the animal,

40 THE LIFE OF THE MOLLUSCA

S Octopods there is no longer any true hell , but only som e simple chitinous rudime nts, to which the retractor muscles o f the head and funnel are

a f D a a Belemnites attached . In cert in ossil ibr nchi ( ,

P . a a etc. , late XXI I I ) the intern l ch mbered shell, ” a known as the phragmacone , is enclosed in ” a a at pointed calcareous she th , or gu rd, the end a f a a opposite to the he d, while rom the dors l m rgin o f the anterior end o f the phragmacone there arises “ a a a a bro d , thin , chitinous pl te, c lled the pro f f h ostracum . To modifications in orm o these t ree

u a a u es constit ent p rt s, or to the partial or tot l s pp r

o f o f a ff sion one or more them , the result nt di erences between the internal shells o f the other members o f

m a a . the order y be tr ced This, however, will be better gathered from the diagrammatic figures on

n . Plate XXIV . than from a y lengthy description

f a N au The shell o the P per autilus , or Argon t

P XXL . P a XXV. . a ( late , Fig 4 ; l te , Fig st nds

ff n f and on a di ere t ooting to the ordinary shell , does not originate in the shell -gland ; it is only formed

f a an some days a ter the creature is h tched, d is

a a peculiar to the female, being chiefly used s

fo r r an d vehicle car ying protecting the eggs , which,

are a a . when deposited, gglutin ted to it It is exo

a and m o f a o f g stric , co posed three l yers, which the

u n re n i o ter a d inner a alike a d prismat c, while the m iddle one is fibrous : there is no pearly layer within . The animal is not attached to it in an y CLASSIFICATION 41 wa an nd y, d the Shell is principally held in place a protected on the exterior by the anterior pair o f a - rms, which are furnished with web like expansions

‘ fo r f a n a the purpose . The ends o the rem i ing rms ,

’ c are m whi h carried folded back over the ani al s body, are tucked into the shell , and s eemingly also assist in retaining it by the aid o f the suckers . It is comm only stated that the s hell is entirely the pro

o f f m n d duct the pair o webbed ar s , a that once the animal quits its tenement it cannot re- occupy it ; but

has bot h statements are incorrect . The latter been shown by actual observation to be the reverse o f f f f a s act , while the occurrence o r ctured hells, showing

s evidences o f repair fro m the inner side , up ets the f m a a n or er st tement , which is otherwise w nti g in

a a probability . The more re son ble supposition is that the shell is m ainly secreted by the m antle cover

a an a m ing the viscer l dome , d that the webbed r s ,

re a fu c which a lso rnished with secretory ells , con

and tribute to the exterior assist in moulding it ,

’ f m a a m during or tion, to the ni al s body. The Cephalopoda are divided into

L : ETRAB A CHIA P Order T R N ( late XXI I) , or those

f n fu having our gills a d an external shell . The nnel

a an d re a is in two p rts, the eyes a open , h ving no crystalline lens .

Sub- 1 : NAUTI OIDEA Na n Order L , or the utilus a d its allies .

Sub- 2 : MMONOIDE A x c Order A , or the e tin t group 42 THE LIFE OF THE MOLLUSCA

a f o f Ammonites an d their kindred , th t rom the close a are parallelism o f their shells , by which lone they

m a u u known , were probably si il r in str ct re to the

Na a n d are f a utiloide , a there ore better cl ssed with them than in a group apart . Order IL : DI BRANCHIA (Plate or those

a an d a m h ving only two gills, the shell gener lly ore

f a n or less intern al . The unnel is complete tube , a d

‘ the eyes have a crystalline lens .

- Su I : DE CAPOD . b Order A, or those with ten arms “ ” o f a a a m a Two these , the tent cul r r s , situ ted on

a S an d a are e ch ide between the t hird the l st pair,

a a an d as more or less retr ctile into speci l pouches , f a rule Only bear suckers at their ree extremities .

r The eight ordinary arms a e Shorter than the body . There is generally a fairly well - developed internal

an d u ua a a . shell , s lly l ter l fins Two tribes are distinguishable : (a) Those (Oigo p sida) In which the cornea covering the eye is in co m

h n a u f . i S irula p let e as a pert re le t This ncludes p ,

n - n - n d a m any o f the Pe a d Ink Fishes, a prob bly

f B Belem noteuthis such fo ssil orms as the elemnites , ,

b M o ida a etc . ( ) Those ( y p s ) in which the corne is

Se i a complete, like the Common Cuttle ( p ), the

m P n - n - s Loli o a d f Com on e a d Ink Fi h ( g ), n their ossil kindred .

Sub- : CTOPODA Order 2 O , or those with eight s m a a m all a i il r r s longer th n the body .

a a fa : a E OGLOSSA These g in ll into two tribes ( ) L I , CLASSIFICATION 43 in which the radula is wanting and the arms are

a m a united by me br ne , while fins are developed on

' m - the body . So e pelagic (Ci rroteuthi s) and deep sea f m O istli oteuthis a or s ( p ) belong here, an d possibly lso

f P a e oct u b the ossil l op s. ( ) TRACHYGLOSSA, the m o f a u u . embers which have rad la, but no tr e fins The Common Octopu s (P olypus vulgaris) an d the r Argonaut a e familiar examples o f this tribe .

Of the interrelationships o f these five classes it is im possible to say much in the present state o f o ur

f u re m knowledge , beyond that the first o r a the ore closely related . CHAPTE R II I

GEOLOGICAL HISTORY

HE Mollu sca made their appearance very early T ’ t an d as in the world s his ory , , might be expected, on the whole the m ore generalized f orm s preceded

m a . ha o f u the ore speci lized It s, co rse, to be borne in m ind that many o f the conclusions here epitomized have been drawn o f necessity from shell characters a an d are a lone, consequently li ble to modification with possible advance o f knowledge .

O f us In the ldest fossili ero beds , belonging to the

a f Lower Cambri n epoch , only a ew representatives f have been found . These consist o some Limpet like shells that have been referred in part (Som alia)

D a an d a Steuotheca P lat ceras to the ocogloss , in p rt ( , y )

ae a a has to the T niogloss . These l st , however, it

u are a a o f been s ggested , inste d, descend nts the primi tive Mollusca (Pro st rept o n eura) that gave rise to the

a . G stropod branch With these is a turreted, con

Rha hi stom a volute shell ( p ) representing the older, or

- o f a n two gilled, section the Rhipidogloss , a d the 44 GEOLOGICAL HISTORY 45

a f B a e rem ins o two Bivalves . One o f these iv lv s (Modi oloides briseus) is known only by the internal ca n a a st , 2 millimetres long, a d ppe rs to belong to

P a the rotobr nchia, or Oldest order , while the other (Fordilla) m ay prove to be a Bivalve crustacean and not a mollusc at all . In the Upper Cambrian further examples (M urchi soui a C rtoli tes Oweuell a and Stua aaolliua o f , y , p ) the

a a are f u as as e rly Rhipidogloss o nd, well one (Trachouem a) sup posed to belong - to the higher one

- — gilled section o f that sub order. Another Gastropod

Subuli tes of u fu af a ( ) do bt l finities , but lmost certainly

Pectin ibranch an a belonging to the s, d h ving a sip ho n o sto m at o us a f f shell , shows th t three out o the our p rincipal divisions o f the Streptoneu ra were already

at a a . a s represented this e rly st ge Alre dy , too , even species o f Cephalopoda had m ade their appearance .

all m m Nau They belong to the ore pri itive tiloidea, an d a -s , with one exception , the str ight helled section o f that group . During the s ucceeding Ordovician epoch the

As ido branch a s m a a p G stropod predo in ted , their r nks reinforced by representatives (Cyclouem a) o f the To p Shells (Turbinidae) that belong to the more sp ecialized

- i c Holo a a and Scali tes one g lled se tion , while p were

s added to the Taen io gl o ssat es. Pelecypods were till

a r branchs Cteno r re, the P o to were represented by douta and m a Filibran chs C ato , the ore speci lized by y

u douta and E opteri a. The epoch also prod ced the 46 THE LIFE OF THE MOLLUSCA

C a first known Chiton (P ai scochi tou) . The eph lopoda had increased in num ber to Sixty-five species of m a - Nautiloidea, the ajority still being str ight shelled, but some curved an d a few coiled forms (the first) are included . With the Silurian epoch a considerable increase

o f M u a in the number oll sc becomes evident. To the G astropods are added members o f the families

Tro chida E ae and Xen 0 ho ridaa A , pitoniid , p . mong

Palaeo co n chs Pelecypods, were most abundant, but

r all orders save the Sep tib an chs were represented. Two more Chitons (Helm iuthoohi tou and Chelodes)

a a a a an d m de their ppe r nce , shells that have been f f re erred, though doubt ully , to Scaphopoda. The

a f a u o f was most m rked e t re the epoch , however, the

f Nau a h a a abundance o the tiloide , w ich then tt ined

u 2 0 h their zenith with abo t 3 species , among whic coiled were almost as abundant as the other shell

forms . From that day the group has steadily

diminished in numbers, only five species now exist

f . ing, or as some reckon them , ewer still The Devonian strata have yielded evidence of the

a P a of further incre se in the elecypods, represent tives f — ae and the Filibranch am ilies Trigoniidae, Pectinid , Mytilidae appearing with the Eulamellibranch

fa — ar in iid M ae—and milies Pinnidae, C d ae, egalodontid a such specialized forms as Pholadella and Allorism ,

the latter being the earliest exam ple o f a Pelecypod, S f howing clear evidence o f retractile sipho ns. O

48 THE LIFE OF THE MOLLUSCA

o f obtained, and the first evidence the highly specialized Bivalve (Li thophagus) that burrows into rock, shell , or coral . At The close o f the P alaeozoic period many o f the at older genera o f Bivalves disappeared, but the a Opening Of the Mesozoic period in the Trias , f number o f others came in . Among them urther ui o representatives Of the freshwater Mussels (U ), f a d o the Thorny Oyster family (Spondylidae), n the am Cam lo Cockles (Cardiidae). The oldest ex ples ( py se i a Aulacocem s and A traoti tes o f of p , , ) the group ten -armed Cuttlefish made their ap pearance at this time . a The Jurassic strata are rich in Molluscan rem ins, which sometimes form whole masses o f rock . The Rhipidoglossate G astropods attained their acme o f

at a e ini r n hs development th t period, while P ct b a c

a a an d a o f multiplied in gre t v riety, represent tives f the higher orms began to appea r. Further remains

o f La H elix . an d a a nd Shells ( , etc ) the e rliest ex mples

f f a Planor is va and o reshwater G stropods ( b , Val ta, Melaui a) have been recorded from the lowest Jurassic a beds, but there is some doubt as to the ex ct determination o f these genera in most cases . In

u erniost e l - the pp b ds, however, the we l known Purbeck

a o f alvata i vi m rble is composed masses o f V , V ara p , etc .

A a r mong Biv lves genuine A k Shells (Area), Anomi a an , d various families o f Eulam ellibranchs, GEOLOGICAL HISTORY 49

C ren idae a including the freshwater y , m de their ap p earance ; while if Corburella be adm itted as a m m a a a u e ber o f the Sep tibr nchi , th t order m st be “ m an d - a added fo r the first ti e . The pens ink s cs o f earlier m embers Of the Sepi a tribe (Bel oteutkis an d

r f u L a Geoteuthi s) a e first o nd in the i s , with the ” ua remarkable Belemnites whose g rds, Often called ” - are f m a f . thunder bolts , a ili r ossils In the succeeding Cretaceous period further de m velo p m ent took place . A ong the Gastropods there

a P in ibr n h was a decided incre se in the higher ect a c s, including representatives o f most o f the families o f

s B m m Rhachiglossa. Among t ivalves two ost re ark able aberrant fam ilies (Radiolitidae an d Hip p urit idm)

x E were confined e clusively to this period . xternally

u m c a s a these look not nlike si ple or l with lid , while

a u m internally they displ y highly pec liar odifications .

Num u Eul am ellibr n chs c ero s other a , in luding some

f m u as P d a an d Saxica i boring or s s ch etricoli e v dae , as as a -fish E nsis a well the R zor ( ), rose , with an undoubted representative o f the Septibran chs (Lei a is p tha). An Octopus (P aleeoctopus N ewboldi ) standing fo r the highest Cephalopods was revealed fo r the

m a u o f M u L a first ti e in the Cret ceo s o nt eb non , but , a m on the other h nd, the A monites an d Belemnites died out . During the Tertiary epoch the Rhachiglossa and

a am the i a a Toxogloss bec e dom n nt G stropods, while the Bivalves Showed an approxim ation to present 4 5 0 THE LIFE OF THE MOLLUSCA

m o f L a conditions . A great ajority the ower Terti ry

E n a ( ocene a d Oligocene) gener still exist , but none

Du u M a o f the species . ring the s cceeding iocene fe are a w species, which still in existence , m de their a a a o f 80 0 ppe r nce , while the Pliocene species or 9 '

a fa a. per cent . re represented in the recent un At the close o f the Eocene the wide distribution o f m a a a o f a m a ny types now ch r cteristic w rm , te per te ,

a a a an d u or tropic l w ters, beg n to be restricted, d ring the Miocene the faun a"bou ndaries o f the Mollusca

a were mapped out ne rly on existing lines . This was more true o f the non -marine form s ; but not till the Pliocene did each geographical province come to m f assu e its present distinctive eatures . CHAPTE R IV

PRESENT HISTORY AND DIST RIBUTION

as u W ITH such a past history j st recorded, it is little wonder that the Mollusca both have been an d are abundant . In 1 866 a rough estim ate gave the num ber o f extinct species as an d living ones as The list has been considerably extended since that

m a fu m a o f f ti e , nd though no rther esti te the ossil f cal orms appears to have been attempted, a recent culation puts the number o f living species known at the end o f last century at upwards o f This total m ay be distributed am ong the five classes as f : a 600 a a ollows Amphineur , ; G stropod ,

a a. 0 P a a a Sc phopod , 23 ; elecypod , Ceph lopod , 47°

Na u a n a a t r lly, too , so ancient a d so numerous r ce is widely distributed over the surface o f the globe

-da and m m a a to y, its embers have beco e d pted to

a r very v ried conditions o f life . The majority a e

a n m arine, and mostly confined to the littor l a d 5 1 5 2 THE LIFE OF THE MOLLUSCA laminarian zones between tide - m arks ; and so f r a f fa a as the seaweeds grow , or to bout fi teen thoms) ; a sm aller num ber inhabit the deeper nullipore or coralline zone ; whilst a few stragglers are met with

all a a u o f at great depths . In c ses the n t re the sea bottom governs their individual distribution . Certain

a forms frequent the rocks, others s ndy or muddy sea

m a flo o rs . So e , on the other h nd, spend their lives in the surface waters of the open sea. The brackish waters o f estuaries an d lagoons are

a few u a u tenanted by kinds, incl ding the str nge p l

m Am hi bola P a V . onate p ( l te XX I , Fig . while

am an d a are - rivers, stre s, l kes the dwelling places o f

a a . On a consider ble number the l nd , every spot

a a o f f a o f M u c p ble supporting li e yields its quot oll sca, and the total num ber o f known terrestrial species is

a and a a consequently very gre t , ye rly being dded to .

AS will presently be mentioned , some fo rms will

a o f a a u norm lly trespass out their regul r h bitat, b t cer tain more exceptional cases o f in terchange between m arine an d freshwater hau nts m ay be appropriately a allu ded to here . Freshw ter Snails sometimes

a a - a become ccustomed to s lt w ter conditions ; thus,

B S ’ at Bornholm , in the altic, pecimens o f Li mua a an d Theodoxi s have been found living in company with m arine .m olluscs in water containing as much as 1 to 1 5 per cent . o f salt . In Southern Algeria M elaui a an d Melanopsis inhabit waters surcharged

a a C fa with s lt , where the m rine ockles iled to survive. PRESENT HISTORY AND DISTRIBUTION 53

Experiments conducted m any years ago show that — a Ph sa species o f the pulm onate genera Lim ace , y ,

lanorbis A nc us— n a a P , and y l ca be h bitu ted by the

gradual addition o f sal t to as m uch as 4 per cent .

u can P o in the water ; so, too , b t less easily , the ros

a i vi ara Bi th ni a an d Theodoxis br nchs V p , y , while the

ta i o an d S ha ri um f Pelecypods Anodon , Uu , p die be ore

that degree o f salinity can be attained. Conversely, marine forms can be gradual ly accustomed to fresh water existence : the Mussel (Mytilus) very easily ;

d um dule C the Cockle (Car i e ), the Oyster, the ommon

L P atella vul ata Turbo ueri toides and impet ( g ), , others, m less successfully . In these experi ental cases, how

ever, propagation would not take place . m On the rocks by the argin o f the sea, within

o f o f reach only the splash o f the waves, or the a at f a o f w ter the highest tides , will be ound cert in — the Periwinkles (Littorinidae) a situation in which they are joined by such o f the Pulmonates as several

f h u - o the Auriculidae an d t e sl g like Oncidium , that

dwell close down by the sea margin .

u - A little lower down, j st below high water mark,

a L - Pu i o a those str nge imp et like lmonates, S ph nari ,

i i a a Guan (Plate XXVI Figs . 2 4 nd and the

A orem odou a recently discovered p , th t have partially

a f are f . reverted to m rine li e , to be ound

B w -m a et een tide rks the Chitons, Limpets ( Patel

K L m Fi urelli ae lidec), eyhole i pets ( s d ), Ormers (Halio

a an d a tid ), simil r molluscs , cling to the rocks or the 54 THE LIFE OF THE MOLL USCA u M u as nder su rfaces o f big stones . The ssels, well

a a their sto ut known , tt ch themselves to the rocks by ,

s s aff byssus threads , their clustered mas e ording secure shelter to many lesser animals ; while in mangrove swam ps the Oysters will attach them selves to the branches o f the trees that dip in the water at high tide— a fact which was observed and

c m a a L 1 6 . re orded by W. S ith t Sierr eone in 72

P a and a eriwinkles, Top Shells (Trochid e Turbinid e), an d ho lo s o m e a a m a o f other t s, h unt the t ngled sses seaweeds ; while among the sipho no st o m es are the

- - Do P P ur ura Do as a . g eriwinkles ( p ), g Whelks (N s ), etc , all stout -shelled forms cap able o f withstanding con

siderable ff i am a . P bu et ng id the w ves The iddock,

P holas axicava Li thodo u n or , S , m s, a d other boring m a olluscs, excav te burrows in various rocks , in coral , f f an d even the shells o their bigger con reres . Others,

Ta es and Coralli o ha a a m like p p g , too l zy to ake their

a a o f u own retre ts , t ke possession the deserted b rrows f o f others . The latter generally selects the crypt o

Li thoelom us a dead , which it Closely resembles in

P a . . 1 n I 8 an d shape ( l te XXXI I , Figs 7 a d ), the

o f u a o f Coralli o ha a Shells s ccessive gener tions p g ,

f u packed one within the other, will be o nd lying ‘ between the valves o f t he original architect o f the

n f home. In the cracks a d crevices o the rocks the

c . m f P O topods hide The ajority o the elecypods,

/ such as - Ta es the Cockles , Ark Shells , p , etc ., remain m th a - h ore or less buried in e s nd or silt , the Razor fis

5 6 THE LIFE OF THE M OLLUSCA

’ examples o f Cbaetoderm a o ff Nova Scotia at

fa li er br chi us was thoms . A Gastropod (Sty f y ) brought up in the South Atlantic from a depth o f fathom s ; a N u dibranch (Bathydori s abyssorum ) in the Pacific O cean from fathoms ; an d some ' Pelecypods also in the Pacific from fathoms ; while a Scaphopod (Dentalium leptoskeles) was o h tain ed from fathom s o ff the south coast Of l f m Australia. Cutt efishes have been taken ro between

an d fa but m u e a thoms , so e nc rt inty

a a a o f tt ches to the records in their c se , since none the form s obtained at these depths were distinctly

- dwellers on the sea flo o r. No hard an d fast line can be drawn between the

a um n m sever l zones above en erated , a d so e species

a m a o f r nge over ore th n one them nevertheless , the

prevailing forms in each serve to distinguish them . Conspicu ous an d most abundant am ong the ocean swim m ing molluscs are the Sea-Butterflies (Plate

. u a XXVI , Figs . 1 formerly gro ped in a class , s

P a u as a teropod , b t now recognized highly speci lized Tectibranchs— those with shells branching o ff from j Bu - he - re the lla like section , while t shell less ones a

- more nearly related to the Sea H ares (Ap lysiidm) .

L a a are P . ess bund nt the Heteropoda ( late XXV I I ,

- Figs . 1 7 now known to be free swimm ing Tm n io

a a gloss , lthough they , too , were once classed apart .

Nu a Ph lli ri 'hoe a A dibr nch ( y ) simil rly specialized, an d ae a I anthina fr the T niogloss te ( ), with countless y PRESENT HISTORY AND DISTRIBUTION 57

o f a a a far f a m ny species, lso p ss their lives rom l nd ,

' h with the larger num ber o f the Cuttl efis es . A more peculiar pelagic assem blage is afforded by m f ‘ those molluscs that dwell a ong the Gul weed

ara u m a o f Nudibranchs (S gass m ). They co prise series ,

f r a a e some O which a e peculiar to the loc lity, T nio

a Liti o a n w L Helci ou gloss te ( p ), a d t o or three impets (

and L epeta). Just as some representatives o f the race have crept

av a down into the depth s , so others h e scended the

an d c m accu m a f a rivers , there be o e sto ed to reshw ter

existence .

In the brackish water near the mouths o f rivers , and occasionally fo r long distances up the rivers

s a f m themselves, some tr gglers ro the marine host

re suc as er thi um Littorina a to be met with , h C i , ,

N eri ta M tilus Cardi um Macom a M a . , y , , , y , etc , where they m ay be fou nd dwelling side by side with fresh

a . u Theodoxi s f has w ter kinds The gen s , o course,

a an d f s a s c re both m rine re hw ter pe ies, while there a

f a a v s o f - as reshw ter represent ti e the Ark Shells, such

Sea hula iuua o f olsella an d f P p p , V , o the iddocks,

Pholas f i vi col an . a, d others

a s a - There is , however, di tinct br ckish water group, including Gastropods belonging to the Ta nio glo ssat e

a P otam ides . ai o f P lu e gener Cert n the a d st rinidae,

' Assem aui a Truueatell Pu m a hi ui , a, the l on te C h a, an d

P u a I hi eui a an d Sc o icu a a elecypods s ch s p g r b l ri . The true freshwater form s consist solely o f C astro 5 8 THE LIFE OF THE MOLLUSCA

a f m pod and Pelecypoda. The or er include some species o f the Rhipidoglossate Theodoxis and its relative Septari a ; Tae nioglossate families such as the Vivip aridae A a ae am la , mpull riid (a completely phibious c n),

Val vatida o f Paludestri n idae M a ae , most the , el niid ,

T hobiidae a n ur ri yp (in Lake Tanganyik ), a d Ple oce da ;

Rhachi lo ssate f as Cauidi a Clea and Nassodouta g orms , , , and Puhn n f m a n r i o ate amilies as Li nae id e, Pla o b da ,

A ae m n ncylid , Physidae, com only k own as Pond

a a 1 Sn ils (Pl te XI I I Figs . The Pelecypoda

Sub- M a a an belong mostly to the ytil ce , d include the

fa U a f a Mu of big mily nionid e, or reshw ter ssels , which the United States boasts no less than about 530 f f species , or more than hal o those known ; with f their kindred the Mutelidae ; the reshwater Oysters ,

E a o f f an m i theriid e , the A rican d A erican r vers ; the

Ran iidae C ren idae an d a g , y , the interesting Zebr

M rei e i . A f ussel (D ss ns a, Pl ate XV , Fig . resh

a i u o a w ter representative o the Veneracea (Gla c my ),

- occurs in South East Africa.

All a f e these, like their m rine con r res, more or less sort themselves according to their surroundings .

- An l Pla . i . 1 and The Limpet like cy us ( te XII I , F g )

a a f Sept ri cling to rocks in swi t streams . Other

a - a Gastropoda hide in the w ter weeds, or cr wl on

B a the muddy banks. The iv lves mostly dwell in

D eissensi a a a f the mud, but r tt ches itsel by its byssus

. m a n f to rocks, etc , in oving w ter ; a d many o the

“ a C ren idw S hawium P X Fi . 16 sm ll y ( p , late VI I I g , PRESENT HISTORY AND DISTRIBUTION 59

and Pi s P . . 6 C a u idi um , late XV , Fig ) limb bo t in the

a r M u a are a f u Weed . Freshw te oll sc lso not in req ently found living in water-pipes an d cisterns connected with artificial supply . Altitude has no terrors fo r the freshwater Mo l

u a Lim uaea Hookeri a a at a l sc , h ving been t ken height

a o f feet above the sea. On the other h nd,

B a m at a depth o f 1 80 fathom s in Lake aik l , so e Paludest rinidae peculiar to those waters have been

ccu o f a met with . The m ost northern o rrence freshwater Snail is that of Aplecta hypuoaum (a British species) which in Siberia attains as far north ° ’ as 73 30 in the Taim yr Peninsula.

m M u ca a u s J ust as the arine oll s bre k their bo nd ,

f a a s an d ssa so will the reshw ter p s theirs, e y to

a L m ae a c m m trespass on the l nd . The i n id e o only crawl on the wet banks o ut o f the water an d in m oist sp ots where swam p - loving terrestri al Pu l

a s m - a Succi nea P a . mon te , like the A ber Sn ils ( , l te XI II ,

. etc. a c . Fig , love to p ss their existen e Among m arine form s fou nd on land m ay be nam ed a m a a P Ci em uocouchus re rk ble eriwinkle , , which occurs

c ffs a s o f u a only on wet li in the Gh t So thern Indi ,

f m f m sea. P thirty to fi ty iles ro _ the Another eri

Li ttori na ar bori cola v s f winkle , , li e on trees ully 1 00

a s f m ac a o f a y rd ro the b kw ters Trincom lee Harbou r, and is never known to enter or be covered by the

a . R hi o do lo ssat e N eri todr as w ter The p g , y , a relative o f Theodoxis u o f m , occ rs on trees so e height in the 60 THE LIFE OF THE M OLLUSCA

Philippines at a distance o f a quarter o f a mile from

f a A m ullari a has an y water . The reshw ter p been

- said to have been met with also on a tree top .

eom elaui a a u a a G , gen s closely rel ted to the br ckish

a Truncatella Is m a . w ter , co pletely terrestri l The true terrestrial Mollusca com prise representa

ive o f a fa Des oenidae t s the Rhipidogloss in the milies p ,

n H dr cen i ae o f ae a Helicinidae, a d y o d ; the T niogloss

A iculid Po m at iida a ae in the c ae, Cyclostom tid ", and lo h ri and o f P a a Cyc p o dae ; the order ulmon t , certain o f the Auriculidae am ong the Baso m m at o

a all m m a . phor , with the Stylo tophora They flourish on every portion o f the habitable land su rface from the margins o f the seas to lofty

a u A a e elevations on mountain pe ks , a Sl g, u d uus, reaching the altitude o f feet in the Him alayas ; while the record fo r farthest north fo r a Land Snail

u a a Vi trina an eli ca wo ld ppe r to be held by g , which is ° a far s a said to extend s a l titude 72 in Greenland .

c i li oides C a He r sti Some , like , the orsic n lix t i s, — an d Testacella (Plate live underground the M f first named entirely so . ost pre er damp situations

o f a an d f at the roots pl nts shrubs , under allen wood,

o f beneath stones, or in the crevices rocks ; many

r f at m o f a a an d S a e ond ti es scending pl nts hrubs, an d do so m ore often than is com m only thought ; other kinds are entirely arboreal . A few that inhabit arid and hot countries can withstand the full glare

f a o the sun s they rest on rocks exposed to its rays .

h E D r In t e gyptian desert . Andrews says that each PRESENT HISTORY AND DISTRIBUTION 61 scattered bush has its com plement o f Helix desertaram. u a (Plate XI I I ., Fig . while the gro nd bene th is strewn wit h the dead shells o f past generations . All the ' terrestrial Snails are chiefly crepuscular or f nocturnal in their habits, but will issue orth on cloudy or wet days . While the hau nts o f the Mollusca are similar in all a o f u of a p rts the globe, the distrib tion the v rious ’ su fa ff as members over the world s r ce di ers, just it

e f a m al do s in other divisions o the ni kingdom , on account o f the differenees o f environment . Obviously the geographical distribution of the “ Mollusca falls primarily into marine and non " marine.

D a m a fouud a e ling with the rine first , it is th t the

r pelagic forms a e the more widely distributed, but m ay nevertheless be described as belonging to polar and N an a tropical provinces . The orth d South Pol r forms differ : Cli oue lim aci na an d Lim acina helicina

f am a are belong to the ormer ; while ong the. l tter Li m aci ta t ca n S iob c na an rci a d poug rau hi a australis.

Ar onauta H aleea Cleodora Cuvi eri a C m b lia . g , y , , , y u , etc , frequent the warmer waters.

f a u The abyssal aun , living nder uniform condi

d e an d a tions, is Widely istribut d, c nnot be broken al e up into provinces , since identic speci s will occur either in northern an d so uthern parts o f the same

ocean or in several different oceans . A few o f the shore Mollusca are very widely dis

a M s M tilus edu is tributed, such s the Common u sel ( y l ) 62 THE LIFE OF THE MOLLUSCA

c va P a . . a an d Saxi a ( l te XIX , Fig but the m jority

and re are more or less restricted, a governed in their geographical distribution by the physical characters

a and u . Of the coastlines, by clim te , by c rrents They are generally considered to be capable o f a a pportionment into nineteen provinces , ccording, f m to the abu ndance o peculiar for s in each . Although these provinces by no m eans strictly conform to the

a o f u n p rallels latit de , they nevertheless ca be con ven ientl a y grouped in clim tic zones , beginning in

a a o f a a a e ch c se with those the Atl ntic Oce n , s f Ma fa 66 ollows (see p , cing p . )

1 . c Ar tic . 2 Bore al North i 3 . Celt c. Temperate 4 . Aleutian .

5 . Atlantic .

6 . Lusitan ean . rt rn At al - i n 7 O Pasp a . siigt rggicai 8. Japoni c .

9 . Californian .

10 . Caribbean . f 1 1 . West A rican

- a 1 2 . Pacific I Tropic l Indo , ncluding the northern o f u shores A stralia. 1 M 3 . exican .

1 . Pa a 4 t gonian .

1 . f 5 South A rican .

1 6 . a a u Southern Austr li n , incl ding the southern u a s o f u a a Tas S btropic l shore A str li , with m a a Ne a ni , w Ze land, etc . 1 P u 7 . er vian .

18. Ma a K a . } gell nic , with erguelen Isl nd

1 . a 9 Ant rctic.

64 THE LIFE OF THE M OLLUSCA

P li catula rassatell a Tridacna Sau ui uolari a and , C , , g ,

N autilus are m cu a a m a . , ore p e li r to the w r er w ters

a h a Contr ry to what as been sserted , there is no

an d a M u a identity between Arctic Ant rctic oll sc , although the prevailing dull appearance characteristic o f M a a a a a i ollusc inh biting cold w ters, s it lso s o f a a m a a f n m byss l kinds , y h ve helped to oster a i aginary m a and rese bl nce give colour to the bipolar theory .

a M u a a r Tropic l oll sc , on the other h nd, a e more highly coloured, some quite brilliantly so .

-m a M a a i far f O The non rine ollusc , h v ng ewer p p o rtun ities fo r individual dissemination than the m a f - m f rine, whose ree swim ing ry are readily trans

a a a a ported long dist nces by currents, h ve n tur lly t ended to differentiate to a far greater extent . The principal barriers to their dispersal are m ountain

a and sea. Ea a o f an r nges, deserts , the ch isl nd y

ff a an fre antiquity o ers its own little assembl ge, d

Th r hoi 'ella quently its individual representative . y op

aute . 2 a V . . 1 8 an d 1 is ( , p 3 , Pl te II I , Figs 9) con

f an u f f fined to the Island o S Thome, in the G l o

Ac ati nella o f Guinea ; the genus h to Ochu , one the

f if as a Sandwich Islands, though it is doubt ul , st ted, each val ley has its peculiar species ; while closely allied forms occur on the neighbouring islands of the

er ou - a group . C i is a well known West Indi n genus, o f which in the main each species is confined to some

a o f a a an d o f single isl nd or group dj cent islets , these

c n Shells the first des ribed , a d only species known to

Li n n mus C. uva P a . Fi . h , ( l te XII I , g is t e sole PRESENT HISTORY AND DISTRIBUTION 65

a Ma o f represent tive in the I sland o f Curacoa. ny the Mediterranean islands have also each their dis tin ctive s hells . Lakes that have long been isolated sim ilarly fu s a m s s rni h inst nces o f p eculiar faunas . A ong t the e

m o f Lake Tanganyika is the most interesting. So e the species there have such stout shells an d p resent such a m arine facies that (with the added p resence o f a Jelly-fish an d other creatures which it had been cu stom ary to associate with m arine conditions) it is not surp rising that fo r m any years it was thought this lake m ust form erly have been connected with

a is the ocean . That ide , however, now known to

u u us ca and fau a be q ite witho t j tifi tion , the n to be a freshwater one that has acquired it s present

Character during a long p eriod o f isolation . More rem arkable instances o f localized habitat are those o f which there are two at least in the British

a L m uwa i n olut f u a m Isl nds . i v a is only o nd in s all tarn

L o f K n on am ountain overlooking the akes illarney, a d

L urne i L c . B t i occurs solely in o h Skene ( Scotland) .

Per c a o f f a a uc as ontr , some the reshw ter gener , s h

Li m acea P lanorbi s An c lus Ph sa Vi vi am Theodoxi s , , y , y , p , ,

- and ui o n a m s u . U , have a l ost world wide di trib tion

o m a On the wh le , however , like their rine kindred, the non -m arine Mollusca are cap able Of being divided according to the prevalence o f peculiar form s into faunas occupying roughly defined areas . Thirty ” are a m a one regions , as they c lled , y be recognized, and these can also be conven iently g ro up ed accord 66 THE LIFE OF THE M OLLUSCA

a ing to the clim atic zones they ap proxim tely occupy, further distingu ishing between those Of the Old and

N f Ma fa the ew World, as ollows (see p , cing)

N ew World. Old World.

u a 1 . a a Circ mpol r 2 C nadi n , a an d N u a 1 . Septentrion l orth incl ding Al s m Te perate kan .

2 . Atl an tidean i er 3 . C i r ca Med t

f . ramean Northern 22 . Cali ornian

a u ca . . 4 . Centr l Asian S btropi l 23 American

5 . Chinese a a 6 . J p nese f a 7 . A ric n , West

8. f ca a A ri n , Centr l an d E ast M l 9 . a agassy f - 1 0 . A ro Arabian

1 1 . Indian 2 4 “ 1 - 2 . Indo Chinese 2 . a l m‘ - Ma a s a f 1 3 . Indo l y i n i a1 2 2 olur fiIan . P Trop c C n 1 4 . hilip pine 2 7 “ PeruVIan . u - M a a 1 5 . A st r o l y 28. Braz Il l an . an d sian , Aus f t ralian , N . o ° 2 0 S . u P uc 1 6 . A stro oly sian P s a 1 7 . olyne i n 1 f a u 8. A ric n , So th f 1 . u a a . O 2 . . 9 A str li n , S Southern 9 Chilian ° 20 S . Subtropical 30 . Argentine .

20. New Zealand South Non e 3 1 . Patagonian . Temperate (No non -marine Mollusca are known from the true

Antarctic Reg ion .) CHAPTE R V

F ABITS ETC OOD , H , .

HE food o f the Mollusca is quite as varied as

their habit o f life . That most o f the land Mollusca are vegetable f s s eeder is only too well known , but the wor t offenders are certain o f the Slugs that bury by day an d only em erge to their feeding -grounds by night ;

a a su f and co n while the l rger kinds , th t scorn bter uge

a us o f a m f u sequently be r the on the bl me , ore req ently

f fu an an d c f . eed on ngi d lichens, reje t green ood Som e other Land Snails prefer decom p osing vegeta

. L s and s a u a tion The Chitons, imp et , holo tom to s Se

u Snails are nearly all vegetarians . In proc ring their food these vegetable consum ers rasp the surface o f

a u a u a and as m the pl nt tiss es with the r d l , they ove

f as e a a a al ong, eeding they go , th y le ve tr ck behind

L m m a f them . The marks left by i pets y requently be observed on the rocks o ff which they rasp the

m a a m a a m a s ll lgae, while the si il r tr cks de by Snails m ay under favourable conditions be seen on palings 67 68 THE LIFE OF THE MOLLUSCA

f a o f etc. m or the b rk trees , At ti es these eed ing tracks present quite remarkable patterns ( Plate

A large number o f m olluscs enj oy a mixed diet .

l s are f o f a a f d an d Nearly al the Slug ond nim l oo , som e will invade the house in search o f fats and

a and . M a o f so p , even milk ny the Helicoids , especially those allied to o ur own Cellar Snail

P oli ta callari a as as m a o f a a ( ), well ny the W ter Sn ils , are also mixed feeders .

- B a an erm etus The iv lves , too , d fixed species like V

P a X. . Hi J ou x M a ilas P a . ( l te , Fig /p y , g ( l te XXVI I I ,

. an d a h a R i z oc i us a XL Fig prob bly t e dult h li l (Pl te ,

Fig . subsist on the microscopic animals and plants bro ught to them by the currents which their ciliary apparatus perpetually excites . Nearly all the siphonostom atous G astropods are

a u an d f c rnivoro s , eed on either dead carrion or

. s B ucci num on other shellfish The Whelk ( ,

P ur ura N assa an d a u ati oa p , , the holostom to s N , by means o f an acid secretion either in the saliva or from a special gland (as in N ati ca) an d the aid o f the

a a r dul , will drill holes through the Shells o f Bivalves

o f a or the upper whorls G stropods, and, inserting their extensile snout , devour the animal within . In som e o f those species o f Murex that have a f o f f ringe spines round the mouth o the shell , one Sp ike will be seen directed inwards instead o f out a P a w rds ( l te XXXI I . , Fig . This is employed by D 6 B ETC. FOO , HA ITS , 9

- B a the Murex as an Oyster knife . The iv lve prey,

f - generally one o the Ark Shells , is gripped in the powerful foot o f the Gastropod an d its shell margins pressed against the spine till the latter is driven between them like a wedge an d the valves are forced a a Murex can and p rt , when the insert its proboscis

an devour the luckless occupant at leisure . The str ge c t i u P a XL spine in a like position in A au h a ( l te ,

m a a a . S cot us Fig . 2) y serve simil r purpose y yp

a . . 1 2 can a u ( Pl te XXXI I , Fig ) grip Ven s Shell while it deliberately chip s out an Opening with its own

a s Shell in the m argin o f the Bivalve . It will l o insert its own shell between the Open valves o f the Oyster and thus keep the Bivalve Shell open while it devours

' a a . Sca hauclei f B a the inh bit nt p eeds on iv lves , which

a s c u m it sw llow whole , r shing the between t he i a a a ts a P a . c lc reous pl tes with which gizz rd ( l te II I ,

an d 1 0 a . Neo m en ian L am Figs . 9 ) is p ved The s, el . a ae an d m Nu a l riid , so e dibr nchs, browse on the c a s an u Ch erm or l , Sponges , d t nicates . The mt o d s an d Scaphop oda thrive on m inute forms o f anim al

f an d m ud c f li e in the ooze whi h they requent . In the op en sea the Pteropods also fare Off m icro

a sm s I an thin a P a . org ni , while ( l te XXX , Fig .

' Carinari a P a . s . 20 an d Fi i ola ( l te XXVI , Fig , a ac - a i ai'i a tt k the floating Jelly fish . C r u will also

ca u fish fo r Mr . Ma a p t re , rtin Woodw rd an d the writer once took from the interior o f one individual 70 THE LIFE OF THE MOLLUSCA

a as a six small fish , each nearly s long their coll psed captor . Among Pulmonates the mos t remarkable carnivores

r - a Testacella f a e the Worm e ting Slugs ( ), which ollow m f their prey underground . Their ethod o f eeding is

fo r a a m peculiar, on coming in cont ct with Wor the

a a an d im r dul is shot suddenly out , the victim, thus

a a f a p led on the b rbed teeth thereo , is dr wn slowly

’ an d irresistibly into the Slug s m outh and gradually s wallowed (Plate Other mem bers o f the

’

u Testacella , as Oleaczm gro p to which belongs such , N atalim z as as o f Po i te an , well some species l d

R um ina decoll ta a (Plate XI I I Fig . are essen iall f t a a . y c rnivorous, eeding mostly on other Sn ils The ocean -dwelling Cuttlefishes and Argona/um are a a o f m u an d the most r p cious olluscs , p rsuing f devouring fish , while the Octopus rom his lair in the rocks will reach out a long arm and capture fish

a fo r a an autil or cr bs his me l , d the N us will take any kind o f animal bait . Of external physical conditions the one most

ff a f m a ecting the Mollusc is the presence o oisture .

u s f r Witho t that , exi tence is o them impossible . Even the Desert Snails cannot support life without oc a a f i u c sion l re resh ng showers , or moist re in the

A m a af a shape o f dew . s rt shower ter dry period will bring the terrestrial Snails out in such numbers — from their hidi n g places at the roots o f grass and plants as to give rise to the belief that they some

7 2 THE LIFE OF THE MOLLUSCA

a r are The limits o f m olluscan endur nce , howeve , ° F. and a said to be a maximum o f 5 2 C . ) ° minimum of 3 C .

a o f a Seasonal ch nges do not , course, c use such slow movi ng creatures as molluscs to migrate, as birds and some mammals do ; but their appearances and disappearances in a given locality m ay generally a fo r as a o f a be ccounted , in the c se pl nts, by the prevalence o f favourable o r unfavo urable conditions leading to their rapid multiplication o r the converse

a a . C a in the are under consider tion eph lopods, a a a o f m a perh ps, being more c p ble locomotion , y a a and migrate along co st , the observed departure and reappearance o f the Octopus m ay in part be due to this as well as to causes connected with their eu viro nm ent affecting their multiplication . o f a a a are The extremes se son l ch nges , on the other a f r a a h nd, o the most p rt p ssively resisted . Some of the more active marine forms m ay in very cold wa weather retire into deeper ter, but the ordinary freshwater kinds simply burrow into the mud and pass the winter in a torpid state . On the land the Slugs burrow into the earth and form a small chamber which they line with mucus ; while the

a Sn ils bury themselves in the ground, or hide under d a a an a fu e d le ves d veget ble re se, sometimes singly, an a o f d sometimes, as in the c se the common Garden

Snails, in colonies . The most remarkable hiber u a a a s are cul , or winter bode , , however, those formed D B TC. FOO , HA ITS, E 73

s in heltered positions in lim estone rocks, where by frequent resort the Snails in course o f years erode

a burrows in the stone, which in pl ces becomes

m all s - a honeycombed by the . In the e resting pl ces they either fasten the m outh o f the shell with m u cus

’ m - to so e object or to a fellow Snail s shell or, when

s a c a f a film of i ol ted , lose the perture o the shell with dried mucus to exclude the cold an d retain their own ” m . a oisture This film is known as the epiphr gm , ” h bern ul m an d h s sua m a or y ac u , a u lly a s all perture

f i - c le t near the centre as an a r passage . In very old

a as an im al s f we ther, the retreat arther into its shell ,

f m a s n m it will or econd a d even a third ep iphrag ,

a s a a a with p ce between e ch . In som e cases such s

m a a Helix om atia a m i s the Ro n Sn il ( p ), this epip hr g im pregnated with lim e salts to such an extent as to

a a am f m m ke it quite solid lid (hence the n e , ro

om um a . a La a s a o f p , lid) The opercul te nd Sn il h ve , c u s a n o r e, only to retre t into their shell a d close the m u u o th with the opercul m .

a an d u n In very hot we ther ( , indeed, nder a y other ady erse conditions) the Land Snails will similarly

a an d s withdr w, protect themselve in identical m anner as a a g inst cold . Freshwater Snails burrow in the m ud a u a P l r i when the w ter dries p , while ano b s m et

Ba a a u with in the h m s, nder these circu m stances

f m s an a m . a a o ercul ates or epip hr g Cert in l nd p ,

C cl o ho ridae belonging to the y p , dwelling in Fu rther

a an d Ma a a a a Indi l ysi , h ve p eculiar p rovision for the 74 THE LIFE OF THE MOLLUSCA

admission o f air during a stivatio n . In some species this consists o f a simple notch in the peristome close to the suture , but in others the notch becomes con verted into a short - necked apertu re placed a little way a back from the mouth , while in yet others distinct

u a a he r t be is developed, either tt ched to t body who l or standing free from it . Molluscs accustomed to hibernation or aestivation probably are longer lived than their fellows ; but as a matter o f fact very few real data exist concerning

a molluscan longevity, which probably varies great

a a r a deal . Many o f the qu tic species a e annu ls, some o f the Nudibranchs require part o f two years fo r

f D ori n their full development . The young o s a d E oli s are born in the summer in the warm shallows

a f o ut a ne r the shore, dri t to deeper w ter, where they f pass the winter , and in the ollowing spring return

a a f a to the tidal rocks, tt in their ull growth e rly in

- an d af a a a . the summer , ter sp wning time dis ppe r

and - a a f The Mussel , Cockle , Ship worm tt in their ull

a P teri a a growth in a ye r , in two ye rs , the Oyster in

- m a fo r ar . five , though in Oyster beds it y live ten ye s

cn a The huge Trida is credited with eight years, while the Swan Mussel (Anodonta) is said to reach twenty

an d a o f a a or thirty, m ny the m rine G stropods probably attain a comparatively great age . The Periwinkle has been kept in captivity fo r nearly twenty years .

L a a are a t he The nd Sn ils mostly bienni l , but D B ETC . FOO , HA ITS, 75

Common G arden Snail (Helix aspersa) has been a f known to survive in c ptivity o r nine years . Less is known about the duration o f life among

a a but a R ossi a n ot the Ceph lopod , it is s id that does

fo r a a a and live more th n ye r , the Octopus not more than four years .

a a o f f m a a are As reg rds ten city li e , ny inst nces on record o f Mollusca surviving under very adverse co n

i io n see a s ante . 2 n m d t s ( l o , p p 5 , 5 3 a d A ong the m ore remarkable the following m ay be cited Speci m ens o f Li ttori na m m 'i cam were kept o ut o f water fo r

n f P a whole year a d then ound to be alive . A ond

Mussel was sent to Dr. Gray from Australia that

i 8 a af as a f m t he l ved 49 d ys ter it w t ken ro pond , having in the interim been only twice in water to see

m e o f Am ullari a if it were alive . Some speci ns p p urposely placed in a drawer in C alcutta were found a af a s e a m a live ter five ye r , despit the w rm cli te .

are m a Those molluscs, however, which ost ccus “ ” t o m d um m o ff e to s mer sleep seem to co e best , and Land Snails will stand months and years o f close confinement without food .

o f H eli x Veatchii f m a is A sp ecimen , ro Cerros Isl nd ,

f fo r said to have existed without ood six years . The

a a is - most striking inst nce, perh ps, the well known

o f s m o f H elix desextorum f m E one the peci en ro gypt, th at was stuck down on a tablet in the British

Mu m Ma 2 1 8 6 an d f Ma seu on rch 5 , 4 , ound on rch 7 ,

1 8 0 a : l a an d 5 , to be live re e sed revived, it lived in 76 THE LIFE OF THE MOLLUSCA

m a r confinement through two su mers , bec me to pid in

an as f u a Ma October , 1 85 1 , d w o nd to be de d in y,

m P a . . was 1 85 2 . This speci en ( l te XI I I , Fig 34) Ma f r P . a a o figured by D . S . Woodw rd in his nu l

M u . . . the oll sca. The Rev A H Cooke collected

am f E 1 0 and ex ples o this species in gypt in 9 4 , kept

m a f . a a 1 1 2 the in tin box without ood In j nu ry, 9 ,

a a ur ten individu ls were still live , but only three s

f Ma a f ha vived by the ollowing rch , lthough ood d been supplied to them . There is a record in the Philosophical Transac tions fo r 1774 o f som e Snails that had lain by in a cabinet fo r m ore than fifteen years resuscitating on

a a a being placed in w ter but , despite the det iled st te

n a a was ment a d ssertion th t no error possible, the narrative does not seem credible . Such dainty morsels as molluscs are naturally

n L a m an relentlessly pursued a d devoured . e ving

f u a a a f a o ut o the q estion , m ny nim ls rom the Wh le to the Mouse prey on them . A Monkey (Macacus cy nom olgus) has been seen to

s o f feed on Oysters , the shell which he broke open

a e o with a stone . The Right Wh le devours n rmous quantities o f Pteropoda with other pelagic creatures ;

a a a u an d a a u the C ch lot , Gr mp s, other Cet ce , devo r

a u s B a o ut o f C uttlefish . The w lr s dig iv lves the

- s sea flo o r s an d a h m . ilt on the with his tu ks , e ts t e

s Ba a s an m s Otter , dgers , R ccoon , Ichneu on , variou

a s an d M c as w as an R t i e , ell Hedgehogs d Shrews , F D B E TC. OO , HA ITS, 77

an d v f as m . e en the Coyote , will e t on the Very 1 m any birds besides the Thrushes p artake o f L and

a s Sea s an d sea- s Sn il ; while Gull other bird , with

f a at f r m s Crows, will or ge low water o the arine kind ; an d m s ca m so etime , rrying the inland to devour , will drop the shells in places where they m ay well p uzzle

fu u s s s c . a s Duc s t re geologi t by their p re en e Sw n , k ,

an d a - s f f a Geese , other w ter bird eed on reshw ter

- M usca s c a l u . m s oll , e pe i l y the yo ng ones Slow wor are very fond o f Slugs ; Frogs an d Toads less so ;

N s a f a a s . s c a ewt will t ke reshw ter Sn il Fish , e pe i lly

m a s m a a . The rine one , consu e l rge qu ntities Cod ,

u a f- fish Mu an d G rn rd , Wol , even the llet Sole , to

am a few m a ff B n e , ke their diet o ivalves ; while the

a ac an u Conger will tt k d devo r the Octopus . Am ong invertebrates their worst enemies are their

as a a . a s own kindred, lre dy noted Cr b will break open the shells o f yo ung Oysters to get the animal

a within . Cert in in sect s seem to select Snails fo r

- their victim s . The fe m ale Glow worm (L ampyri s n octi uca t l ) attacks an d kills H elix ne m om lis. S aphy lim i s oleii s has been seen to set upon and kill the Heath Snail (H eli cella i tal x) ; an d the larva o f a B Drillus avescens assa a nother eetle, fl , will even ult

a u a P om ati as a l nd operc l te ( ), watching till the Sn il

u f a i s a begins to iss e orth , nd then with t strong j ws

1 Tho ugh Bl ackbird s are co m m o n ly credited with also ea in Sn ail s it is ver o u ul if the reall do es eciall th e t g , y d btf y y , p y ar kin l ger ds. 78 THE LIFE OF THE M OLLUSCA cutting the m uscle that attaches the operculum to af the anim al to prevent its closing , ter which it proceeds to devour the animal an d undergo its meta m orp hosis within the shell . Some species o f Silpha m m a an d a seize s all Helices in their ndibles , bre k the shell by throwing their head back and striking it

a a o f ochleocto against their p rothorax . The l rv e C nus vom x ff prey on di erent species o f Snails . The big Water Beetle (Dytiscus) an d other water insects live a l rgely on Water Snails . To what extent larvae o f Flies thrive on living Sn ails does not seem quite

M e o certain . el m phom heli ci vom appears to be para

o a H e ella c N siti in Fr nce on li c onspuxcxta. In orth America Sarcopl mga heli cis has been bred from P oly

m th roides an d n om i a. m o m m f m a gy y , Cy y rtuo ro de d

an oll Snails . W d ecki u achatim e has been found run

Achati na L a b t ning over living in iberi , u whether they are parasites or not does not appear . Small m olluscs are swallowed whole an d the animal digested out by Sea Anem ones an d Starfish . The

a i - l tter, too, is very destructive n Oyster beds, open

a a f m a ing the v lves either by m in orce or other e ns , an d a and a s then , everting its stom ch p s ing it between

a and a s . the v lves , it digests bsorb the mollusc Among molluscan parasites the most abundant belong to stages in the developm ent o f Platyhelm in

a W s m f thi n orm , which co plete the cycle o their

s a a exi tence in some other nim l , such as Birds , Fish ,

. f Frogs, etc The history o these is completely

80 THE LIFE OF THE MOLLUSCA t acean s o f different sorts (Ism aila and Splem clm o txophii s) are to be found on Nudibranchs ; another

a o f I anthimz attaches itself to the flo t , which it

ot e e m atches in colour . Ostm c h r s lives in the gills o f the Giant Clam (Tridacna) ; while Pinnotheres takes up its abode within the shells o f several

ff al c u the a a di erent Biv ves, in l ding gre t Pe rl Oyster,

ha a f u an d one species s l tely been o nd in Strom bus . A quaint little Mite (Philodrom us lim acum) infests terrestrial G astropods . It lives in the breathing

m a f ch amber, and y be seen issuing there rom and r unning with great rapidity over the body o f its

a m a host, but wh t its connection with the mollusc y be is quite unknown . Another kind o f Mite (Atax) a is found on freshw ter Mussels . Clear cases o f com mensalism on the part of molluscs with other animals are those o f certain o f the Pelecypods : M odi olari x m arm om m lives in the

o f A c an M on tacuta Le t integument s idi s ; , p on and

Sci obereti a dwell with Echinoderm s . j ousseaumia is commensal in the chamber o f a Sipunculid Worm

s idosi hon lf m a (A p p ), which is itse co mens l in the coral

c athus an H eter sa . genera Hetero y d op mmia. Ley an squam osum resides in the burrows o f Annelids and Crustaceans ; Ephipjaodonta is com mensal in the burrow o f a Prawn ; Vulsella lives in the substance

o f . a M a ilus Sponges The G stropod g , which takes

a a m a an up its bode in cor l sses , d probably supports itself on the Infusoria an d ot her small animals which D B ETC FOO , HA ITS, . 81 the coral polyps draw towards themselves by their

a a . a cili ry ction So , too, prob bly do its close rela tives Com lli o hi la L e toconcha an d R i z c p , fi , h o hilxs. The last nam ed in its adult state attaches itself to the

a o f An ti atkes an d all m br nches p , but closes the outh

o f P a XL . its shell ( l te , Fig

m o f B a a uc So e the iv lves, which bore into cor l, s h as Com lli o ha a an d Li thodom us m a a m a p g , y lso si il rly

s ua profit by their it tion .

Whether the occurrence o f the sm all P lan orbi s- like

Cochli ole i s c was f u a a p , whi h o nd in Ch rleston H rbour u a o f A coétes was a ca nder the sc les the Annelid ( ), se o f commensali sm or parasitism has not yet been m ade clear . Several m olluscs are them selves parasitic on other creatures : Starfish an d E chinoderm s are p eculiarly

a a as . Stili er P a . li ble to these p r ites f ( l te XXVI ,

an d R obi lla di a s Fig . 2 7) r ne tle among the spines o f

E m s f m an d Stili exin a chinoder , while both the or er f

c u d s o f a s an d Th ca o cur b rie in the kin St rfi h , y , one o f Ca ulidae a ac s s f the p , tt he it el to the under side o f

a s . f u c s o f the r y These eed on the j i e their host , which they absorb through the long proboscis they

m Sea- u um m insert into their victi . The C c bers co e

o ff fo r are u s m a even worse , not only they th s i il rly a u but aff m ttacked from w itho t , ord lodg ent within

- — a a o f o uc . E xtoval va a to v riety bl od s kers viz , ,

P . . Bivalve ; E uli m a ( late XXVI , Fig a relative

f t li e n o f a a t o S i f r a d a series other G stropod , Ex o 6 82 THE LIFE OF THE M OLLUSCA

con cha E x-tocolax En tosi hon an d E ntexoxenos . , , p , etc ,

are u an d whose exact relationships nknown , whose

a f are a appearance, so tr ns ormed they , suggests lmost an y vermi form animal rather th an a Snail . One instance has also lately been placed on record o f a m ollusc (Epi stethe gonoductyli ) parasitic on the ven tral surface o f a Stomatopod crustacean (Gon odactylus m m chi gm ) fro shallow water in the Persian Gulf. A more interestin g form o f parasitism is afforded

a f - o f f a M in the e rly li e history the reshw ter ussels , an d it is said in that o f the marine Bivalve P hilobi'ya

u Mu also . The yo ng ssels are hatched between the

- f o f a an d a a gill olds the p rent, , h ving p ssed there

u a a u thro gh the veliger st ge , esc pe thro gh the ex current siphons"opening in the form o f a peculiar " a a s l rv , which when first ob erved , being thought to

a a am o f be dist inct cre ture , received the n e

lochidi u P a . a a has a G m ( l te XXIX , Fig . This l rv hook in the middle o f the margin o f each o f its two

a s m are f a an d a a v lve , which , oreover, per or te , lso long

a o f an byssal thread . It is incap ble supporting

s nd a as has independent exi tence, a c nnot , been

a a an d st ted , swim by r pidly opening closing its

s - a a valves . Thi valve clapping t kes pl ce vigorously

if a c m a h ff o f f fish o es ne r, an d as the e ect orcing the

bys sus straight o ut . Should the latter touch the

a . a e fish , it dheres to it Any ch nc movement then bringing the Glochidium itself into contact with the

fish m m a s a s . if a it i edi tely n p to The hooks , the p rt D B ETC. 8 FOO , HA ITS, 3 seized be a soft portion such as a fin or a gill -fila l m a t he n ent , penetr te tissues, a d the irritation they set up causes an overgrowth o f the skin o f the fish to

l um c s c enve op the Glochidi , whi h thu radled thrives

r m fo so e two to six weeks on the j uices o f its host . Meanwhile the byssus an d adductor m uscle o f the Glochidium disappear an d the two perm anent

f r adductors o f the adult an d the oot a e developed .

s a m The m antle secrete new shell , rese bling the a f a Glo chidium shell dult orm , bene th the , which

fi s s fo r f u af persi t , however, three or o r weeks ter the young Mussel is again set free by the perishing o f

a . B m u a the cont ining cyst y the ti e , tho gh , th t it quits this tem porary abode an d proceeds to com plete

has a m a ca far its growth , it l ost cert inly been rried from the place o f its origin to som e spot where perhaps there will be more room for it . Overcrowding is undoubtedly as bad for anim als

an d a n m as it is fo r plants , in the veget ble ki gdo various well -known adaptations are p rovided to insure the dispersal o f . the seeds an d their convey

M usca s a c ance to fresh soil . Among the oll the in t n e just cited is perh aps the m ost distinct exam ple o f a

m a M us a like p rovision . With the rine oll c the shifting waters o f the sea are practically the sole vehicle fo r the transportation o f the young to ne w

and m o f a all c u s spots , the e bryos ne rly , in l ding tho e

are a u s a are that , like the Oyster, fixed in the d lt t te,

s a fa o f sea . free swimm er , princip lly on the sur ce the 84 THE LIFE OF THE MOLLUSCA

N of fr are evertheless, when such millions y pro

i n m . and duced by even a single parent (see f , p

fo r a all committed to a sole agent dispers l , it is evident that the greater nu mber will be carried in

a a an d a one direction and to a single re , th t the shorter the tim e before they settle down the greater will be the n um ber thus congregated together . To this fact must be attributed the large assemblages o f

a M and one species , such s the Common Shore ussel , not to an y wish for a gregariou s or social life after the m anner frequently displayed by animals higher m in the scale o f organization . To their li ited capacity fo r locomotion is similarly attributable

c f La M u a. Ea fo r f the olonies o nd oll sc ch lives itsel ,

f f r f a com peting with its ellows o ood, the abund nce or dearth o f which principally determines their

m u o f co -O a m a nu bers , witho t thought per tion or utu l assistance . ff f r What the currents will e ect o marine Mollusca,

' a o f a and the running w ter stre ms rivers , especially

f fo r f in times o flood, will do the reshwater ones and more, since during floods not merely the eggs and

ff a a o spring, but the nim ls themselves, will be borne a a f u w y to resh spots by the r shing current, and, as f the waters subside, be le t in ponds and ditches that are otherwise disconnected . The colonization o f

m a a s o f per nently isol ted piece water, and even the

- a f dew ponds on high hills , part rom accidental im

o rt atio n m an ff p by , is e ected by other agencies o f 8 F D AB S ETC. OO , H IT , 5

B s dispersal . Not infrequently lar e Wa r eetle g “ te have been captured in flight from one piece o f water a a a carr n m o lluscs to nother th t h ve proved to be i i g w y Of m o re B a attached to them . It m ay be one iv lve

a f a Shells holding tight on to the legs, or reshw ter

- L m Anc lxs a w1n as . i pet ( y ) or two , dhering to the g c es The fry o f other kinds o f Snails m ay be readily

a s a -f an d tr n ported in similar fashion . W ter owl Wading Birds have likewise been taken with

B a a f an a iv lves dhering to their eet , d h ve been observed to fly Off with water - weeds clinging to them that might well bear both sm all kinds o f shells

n u s m a a a s a d o va. Yo ng Sn ail y lso be tr n ported ’ a a o f sticking to the bird s plum age . On the rriv l the insect or bird at a fresh piece o f water thes e in

u a a ff n wa f vol nt ry p ssengers drop o , a d in this y resh colonies are started . Land molluscs an d their eggs adhering to vegeta tion are carried down by flood waters an d stranded m f m on subsidence in fresh pastures . S all or s dwelling in swam py ground an d o va m ay further more be conveyed to distances in the m ud sticking

’ s f c f a s a to bird eet , or linging to their e ther , especi lly if the birds be such as roost on the ground .

m n an Transport by a , both intentional d acci

a a s a u dent l , h rdly enter into consider tion here ; b t it is interesting to rem ark how the com m oner and hardier European Slugs and Snails have been intro duced near ports o f call in many widely separated THE LIFE OF THE MOLLUSCA

parts o f the globes such as the C ape an d Australia.

a f P rob bly , too, the uni orm distribution round the shores o f the Mediterranean o f the commoner sorts is due to the existence o f trade in the area from very early times .

88 THE LIFE OF THE MOLLUSCA

ni o b u tu idus an d L am si li s U atav s, U. m , p , in which the

a an d fem ale is rather broader than the m le , in

Astarte o f s , in which the border the hell is smooth

m a but u a f m a . in the le , cren l ted in the e le Am ong the Cephalopoda sexual dimorphism is

v m a s a au f m a ery rked , e peci lly in the Argon t , the e le o f which m ay attain to fifteen times the length o f re the m ale . Generally the m ales a more slender

a f m a a t lu o f th n the e les, but in N u i s the hood the anim al an d the m outh o f the shell in the m ale are

a m a u fi wider th n in the female . The le C ttle sh is also rem arkable fo r the curious m odification o f one “ ” o f a m as a P a its r s , known hectocotyliz tion ( l te

. . o f s arm XXV , Fig At the time pairing thi

m n beco es charged with the spermatophores , a d is

f r the vehicle o their transference to the fem ale . In

m a — as fo r am a — so e c ses , ex ple , the Argon ut the hecto co tyl us becomes de tached from the m ale an d is able

and a fo r a a to live move bout consider ble time . It

has a even been described as a p rasite on the female . — Most o f the Mollusca are oviparous that is to

sa la a fe c a y, y eggs ; in w ases the eggs h tch within

o f and are the body the parent , the young brought

f a as Calistoohi tou a orth live , in mong the Amphi

u M el ani e: n V vi u P a a d i m a . . ne r , p ( l te I I , Fig 7)

am f a a mbal ong reshw ter G stropods , Cy and m any species o f Li ttoif iua am ong m arine ; several isolated instances also occu r am ong the land Pulm onates e. . P ram idu u O ens s P u a g , y l , p , ome pillid e , etc . In the REPRODUCTION 89

Clausiludae the eggs are also som etim es extruded

f a a s B aleu P a X be ore hatching, s h ppen in ( l te I I I

1 usilia f. Fig . 8) an d some species of Cla itsel a The eggs are isolated in the Amphineur , the

a a a a and more primitive G strop od , in the Sc phopod ,

m o a a the Pelecypoda. In the ajority f the qu tic G astropoda they are either enclosed in tough cap

m a ar as Pur um sules, which ay be deposited p t ( in p ),

a P a X . or in irregul r clusters (as in the Whelk, l te X X ,

Fig . Or the spawn consists o f large numbers o f a u a a us m a a eggs ggl tin ted in gel tino sses , or spre d o ut f in the shape o a strap or ribbon , in which the “ a a eggs are arranged in rows . This nid ment l rib bon is sometimes coiled u p like a watch spring and ustoui attached by one o f its edges f oruuuu j oh ,

a Sea u P a . . am a Sl g, l te XXX , Fig The nid ent l

f r capsules o the Cuttlefish a e clustered like grapes ,

a bu s q thiua e ch containing t a ingle embryo . In ,

Sea a e a are a the purple Sn il, the gg c psules c rried a closely p cked on the u nder side o f a raft or float , f b a an d n ormed y the p rent , attached by one e d to f P a X . . her oot ( l te XX , Fig The number o f eggs laid at a time varies in the

ff a P a. di erent species, but is gre test in the elecyp od The Swan Mussel (Auodouta cyguam ) has been com ’ p uted to lay from to the Painter s Mussel ( Uui o pi ctorum ) the Common Oyster from to over while a large American

m a has a a Oyster y, it been s id, cont in more than 90 THE LIFE OF THE M OLLUSCA

o a. su v A portion , pposed to be one seventh o f the Ovary o f a Ship -worm (Texedo) was

m a esti ted to contain eggs . For Chiton

u u Loli o and is q oted . Among C ttlefish g Sepi a are said to have to A single nida mental ribbon o f the Sea Slug (Archidoris) has been reckoned to enclose to The single

a u o f Pu m la ill s— n a c ps les rpu p u a d one individu l, it

a has o f is s id , been observed to produce 245 them

a f 00 600 o f a cont ins rom 4 to eggs , which , perh ps,

1 0 1 6 a m u a only to ttain at rity , the rem inder serving

as f a . Pu a a . their ood while in the c psule The lmon t la m y co paratively a small number o f eggs . The f a L m A 6 Li m uceu reshw ter i pet ( ucylus) lays only 5 or , an d P lano is rb 20 to 1 00 in each mass . The common

a G rden Snail (Helix aspexsu) produces 40 to 100.

a f a a f Vi vi am The vivip rous orms ver ge ewer, p bring

f a 1 an d Sten o ridae a ing orth bout 5 , the gy bout 4 or

6 . The eggs o f m any o f the Land Snails have a

u a a a an d a o f a reg l r c lc reous shell , re sometimes gre t

o f f Ac at a n d u size , those the A rican h in a the So th

A a Stro hochei lus P a . . 1 a meric n p ( l te XXX , Fig ) riv lling ’ a pigeon s egg in magnitude . In m ost cases the eggs or young are at once a a fa u a b ndoned to their te , b t in some instances partial protectionis extended to them In their early

a a r stages . Occ sion lly the eggs a e attached to the

a . ulei p rent shell This is the case in Li o m esus D , while several species o f Theodoxis and Sepmriu have

92 THE LIFE OF THE M OLLUSCA

abu ndant instances occur o f incu batory retention o f

u u a the yo ng , sually in the sp ces between the gill

f M u s n i o Anodon ta . folds . The reshwater ssel ( U , , etc ) an d the little freshwater Bivalves Spheei'i um and P i sidi um are noted exam ples ; in the two last - nam ed instances there are s pecial brood- pou che s fo r the f reception o f the newly hatched young . In the resh

wa a Mu ha ter Zebr ssel on the other nd,

r the young a e lau nched o ut at once into the water . Among m arine form s retaining the brood are Area

vi vi um P hil obi’ u c m p , y , the Oyster , whi h keeps the in

m a an d - Teredo c the ntle , the Ship worm ( ) whi h

us s m m ho e the in the gill cha ber , while in one

B va Thecali u coucam em tu f m a f m a i lve , , the e le or s Shelly chamber within the margin o f the shell fo r

n f the reception a d protection o the young . The early stages in the development o f the young

Mollusca are the sam e as in all other an im als . The

a c s m a cell s, un til origin l ell plits up into ny , the result

u u ing m ass looks like a m lberry . The constit ent

are u ua cells , however, neq l in size, one series , the

f m m a es a a first or ed, or cromer , being l rger th n the

m m an d a m u others , or icro eres, l ost s rrounded by

s a them . Thi disparity in size is less m rked in

m f L bu pri itive orms like the impet, t most pro

n u o un ced in the C ttlefish, in which the macromeres

- are most highly charged with food yolk . In the G astropod ovum it is interesting to note that a

u u u a c rio s obliq ity in the cleav ge becomes evident , REPRODUCTION 93

“ as a c a a an d known the spir l le v ge, that this obliquity takes a reverse inclination in sinistral forms i to that which obtains n dextral . In the succeeding stage o f the development the m m c av u f acro eres , whi h h e ndergone u rther sub

s o f o f m u s divi i n , orm the inside lining the lberry , a

an d c a cav u m a it were , en lose ity which lti tely becomes the digestive tube . Other cells arising between the layers o f m icrom eres an d m acrom eres s ubsequently form the variou s organs an d m uscles o m M m ‘ a f the young ani al . eanti e there rises a “ a um swimming org n called the vel . It begins as a ridge fringed with fine hairs (cilia) encircling that part o f the head o f the em bryo which lies in front o f m u an d a a f the o th , it fin lly expands into sort o

sc is a ut s . di , which dr wn o into lobes or into finger “ ” is a a This condition the veliger st ge , which , s a a m a f lre dy re rked , is characteristic o the Mollusca

P a . . i f ( l te XXIX , Figs 1 The stage s urther m arked by the form ation Of the young shell and the

a a m u first ppe rance o f the foot . As the young oll sc

u grows p the velum disappears .

Ma a a f s a am ny l rv l orm , especi lly ong the G astro

a are ff f m pod , very di erent ro the adult both in the a a a c o f a a an d n d a p p e r n e the nim l the shell , a h ve

s as s c a u been de cribed di tin t species , while the d lt

f m o f s m has or o e not yet been ascertained . Thus the young shell o f L um ellm'i a has received the n am e s o f o wni a Culcurellu E chi os i c , , u p m , etc., while Ma 94 THE LIFE OF THE MOLLUSCA

i lli a . . 2 a g vr yu (Plate XXVI , Fig 9) is prob bly the young o f D oli um y and u nder the n ame Sinusigem

P . . 8 a a m o f ( l ate XXVI , Fig 2 ) l rge nu ber the young o f very different genera has been included. To the curious parasitic (glochidial) stage o f the you ng freshwater Mussels an d P hilobryu that succeeds the veliger stage allusion has already been m ade

ante . ( , p There is u sually a m arked difference between the

m c c o f a e bryoni shell protocon h G stropods , pro

u dissoconch o f Pelecypods) an d the ad lt , the junc

a an d in dicat tion between the two being very m rked ,

a au f ing p se in the growth o the shell , during which tim e the you ng animal was completing its growth in

P a . . P a . . other respects ( l te IV , Fig 2 l te XXIX , Figs 1 4 an d The G astropod shell in the very early stages of its form ation is exogastric coiled forward over the — a o f h m P . . 1 C but he d t e ani al ( late IV , Fig , ) it

speedily takes on the right or left spiral o f the adult . E ven in the Lim pet (P utellu) an d Keyhole Limpets ( Fissu rellidae) in their em bryo stages have coiled

s c su a are fu exoga tri shells . The Fis rellid e rther interesting in that the characteristic perforation, beneath which the posterior termination o f the ali m a a a as a s ent ry c n l lies , first appears lit in the m a o f u E m ar inula P a rgin the yo ng shell . In g ( l te f . . 1 s s u VI I , Fig ) the slit p ersi t thro gh li e, the hinder end being con st antly filled up as the anim al grows ;

96 THE LIFE OF THE M OLLUSCA proportionately nearer an d nearer the umbo (Plate

XXIX . , Fig . Another interesting instance o f change in growth

aff f Velates P a is orded in the ossil ( l te XXXII .,

. 1 w u Figs This , hen yo ng, closely resembles a

Theodoxi s eri tina a a a an d N ) in ppe r nce, , like it , grew

u f n m spirally . When abo t hal a inch in dia eter when about four an d a half whorls have been com

l et ed a a n p ), however, it ce sed to grow Spir lly, a d contin ued the lip o f the aperture in an oblique outward

at am m CO io us s direction , depositing the s e ti e p helly m a a c um a o f - teri l on the ol ellar w ll the body whorl , while it obtained the extra room required within by reabsorbing the inner side o f the shell at that point . I n the end the adult anim al is seen to have occupied a single cham ber excavated in previously deposited — shell a u nique example o f m ost uneconom ical m oll uscan architecture . In most embryo Gastropods an operculum is u u f a present , though s bseq ently requently disc rded

P a X . . o . P m a a e ( l te X IX , Fig 5 , ) The ul on t ( xg pt

u a Si ho narudae an d On cidiidae the Auric lid e , p , , which

n cu u l an d Am hi have a op er l m during deve opment , p bolu c u u f , whi h retains it thro gho t li e) do not develop

n u um fu a a operc l ; rthermore , the veliger st ge is reduced or altogether wanting in the m embers of

a i s a e this order, s it in vivip rous sp cies whose young

re c a a hat hed in the adult condition . In those G stro REPRODUCTION 97

a pod which are naked when full grown , the shell falls off soon after the reduction o f the velum . With the arrival o f adult characters come the

n f characteristic m arkings a d sculpturing o the shell , with its concomitant adornm ent o f spines an d pro cesses when such are p roduced in the course o f

f n io n idm . s growth In ome orms, like the U , the

u m yo ng shell is at first wrinkled , beco ing smooth in

a f an d a m a o f u u is o serv l ter li e , si il r loss sc lpt ring b able in som e G astropods certain species o f

tell R os ari a an d Fusus) as well as som e Ammonites .

at a u a f a u s o f fu Arrived m t rity , the fin l e t re the lly f m u or ed shell are assum ed . The yo ng Cowry shell

C rx a ha a a li P a . . ( yp ) s thin , sh rp p ( l te XXVI , Fig which becom es curled inwards an d enorm ously

c an d a u P a V . thi kened toothed in the d lt ( l te ,

. c P terocem P V . Fig The S orpion Shell ( , late ,

tro bu . . l Fig . S m s (Plate VII I , Fig R ostel ewi u

P a X. . A orrhai s P a IL . n ( l te , Fig p ( l te , Fig a d

s v cu us an other , de elop the rio spines d p rojections

a su u m u . Rhi z ocki lus as a a th t rro nd the o th , lre dy

a a f Auti u hes an d a m noted, tt ches itsel to the p t , l ost c uth o f P a XL entirely loses the mo its shell ( l te ,

L n s f m i Fig . The and S ail or a thicker l p or

a a u so n rrow their p ert re with projecting p rocesses ,

a a m a a o ut an th t it is rvel how they p ss in or , d

an u P a . how they c excl de their eggs ( l te VI II , Fig s . 1 4—1 6) 7 98 THE LIFE OF THE MOLLUSCA

In som e other G astropods the final whorls become m ore or less u ncoiled as in Di aphora tuba (Testa

ch odella B uooksi ana P a . cellidae), B ra yp ( l te XXXII ,

1 0 n U ae H selos Fig . ) belongi g to the rocoptid , in yp tom a an d La a as as am , other nd Sn ils , well ong

m suc a Verm etus P X. . 1 arine species h s ( late , Fig 7)

an d Tena odes P a V. . Blwos ira g ( l te , Fig whilst in p echi nus a a f a a the whole shell is sc l ri orm . Then , g in, the apertu re m ay be turned upwards towards the

as Anostom a P a . . 1 an spire , in ( l te XI I I , Fig 3 ) d Hypsel ostom a while the last whorl m ay be carried

u an o f right p d over the spire , as in certain species

O i sthostom a P a . Gi bbus p ( l te XXXI I , Fig. In the body whorl is flattened an d curiously constricted at if h one point, as the shell ad been made soft and

P . . then pinched up ( late XXXI I , Fig Some Biva lves continue to increase the thickness o f their shells by additional deposition to the inner

layer long after they have ceased to grow outwardly.

a r hwa This is especially notice ble in the Oysters , G yp

cuata P a X . . S ond lus an d ax ( l te X X , Fig p y , other

o f s r co i a and attached form s . In the case O t ea cornu p

d l va i u P a . 6 a Spon y us r s ( l te XXX ., Fig ) the dded

a f o f a shelly m tter is not solid, but ull c vities filled

Pholadi dea a a o f with fluid . , close rel tive the Pid

o r P holas a f dock , , fills up the nterior opening o the

- o valves with a callous plate . The Ship worm (Tered ) and some other borers are said to close the end of

their bu rrows when adult . In Nautilus the last

CHAPTE R VII

EVOLUTION

HE study o f evolution in the Mollusca is an

exceedingly complex one . Their extreme plas t icity naturally renders them both peculiarly suscep tible an d readily responsive to the operation o f the two great factors that govern the lives ‘ o f all animals - a f n n mely, the influence on them o their e viron ment and the necessity laid on one and all o f pro

u f . f f fa c ring ood The molluscan mode o li e is , in ct , m ainly governed by the combined action o f these

u n f beco m two controlling infl ences, a d in turn itsel

a fa ing potent ctor, completes the cycle by reacting

a a as on the nim l , ,which is thus impelled , so long

a o simil r conditi ns hold , yet further al ong a given line o f development .

O ho wevei' o f a wing, , to the paucity st ble elements

ac n r to be ted on , continuous progress in a y di ection has a u f , despite the ntiq ity o the race, been slow indeed . The total lack o f anything like internal framework has militated against any such wonderful 100 EVOLUTION 1 01 progress as exhibited in the vertebrate kingdom ; the very plasticity o f these creatures has thwarted

as progressive development , we understand the

a e and a a a o ff phr s , they re dily retrogr de , or br nch , N into bypaths . evertheless , progressive develop

c a a c ment is tra e ble in cert in haracters , while in other conspicuous features the action o f environm ent

ua m a s or individ l require ent lone eems responsible . It will suffice to take certain leading features an d organs to su m m arize what is known concerning

m an d o ut a c us if an the , to point wh t oncl ions , y, can be based upon them . The tidal zone was in all probability the cradle

u ha o f the race, altho gh it s been argued by som e with m uch show o f reason that the earliest form s m were pelagic . Fro the shore the various m em bers

m m n d betook the selves , ostly to deeper a deeper

a but a s u water on the one h nd, l o, tho gh perhaps

an a ua i il m ore tentatively d gr d lly, to fluv at e an d terrestrial conditions on the other .

u m o f a f - a No w, the first req ire ent so t bodied nimal , an d especially o f one considered by it s fellows to be

a . a a e good e ting, is protection In e rly d ys , how ver,

m far f a an d w ene ies were ewer th n now , it as rather from the force o f the elem ents that preservation was needed .

s u m is su Thi first req ire ent pplied by the shell , an d all s a B a an d M three type , Univ lve , iv lve , ulti 102 THE LIFE OF THE MOLLUSCA

r of valve, made their appearance early in the histo y the race .

The last named, the Chitons, first occur in the

h . r Ordovician (Priscoc i ton) They a e, however, a

a an a a a conserv tive race , d have not m teri lly ch nged

- f f r off . l their orm since those a days Stil , taking the

A a a a mphineur as whole , the cl ss shows a desire to disburden itself o f its coat o f mail . Through the successive genera o f one branch of a Acan t ochi tes Am i cula r to the Polypl cophora ( h , , C yp h c i ton and Cr to lax P a X . i , yp p , l te I , F g . 3) the com

' n a and ponent plates become wider a d wider ap rt,

a a f the whole nim l more vermi orm , while in the

- — A a a a X . . 6 worm like pl cophor (Pl te I , Figs 4 ) the has a a a shell dis ppe red , though numerous calc reous

a spicules rem ain scattered over the m ntle .

a a As regards the G stropod , when it is borne in mind that the embryonic shell is nautiloid and exo

n f r a t gastric, a d allowing o the Gastropod peculi ri y o f a and a o f f spir l torsion, the number v riety orms

assumed in the adult state is remarkable . Seeing n f that departures from this embryonic , a d there ore

are a primitive, type pronounced, even in the e rliest a a far known G stropods, it is not possible to s y how environment or other forces m ay have played part

in their development . Certain elongate forms o f

f Tere P a o bra a . shell like th t ( te XI I , Fig . 5) would

a a a a seem positive dis dv nt ge to the animal . Never theless a a a a , cert in bro d ch r cteristics are observable.

104 THE LIFE OF THE MOLLUSCA

M o f o f e e their kindred. ost the members th s groups

ar are furnished with thick opercula, which e not

withdrawn far within the m outh Of the shell . With

fo r a f r the capacity, however, retre ting u ther and f and o f i urther into the shell , so out the more m

a a o f a o f O medi te re ch d nger violent injury, the per ul m an a c u , always encumbr nce, tends to become less

and less ponderous . Other inter -tidal forms belonging to families

u a a a al higher in the m oll sc n sc le h ve so, under the

a a necessity o f f cing simil r conditions , developed

are Li ttoxi na P ur ura ass strong shells ; such , p , N a,

an d a a a P terocei'a Turbinell a n , mong tropic l gener , , , a d

trom bus a a S . The l st n med , indeed, is the most

f f ll a di ficult o a shells to bre k , resisting even the lusty

application of a geological hammer .

f Is ui fa When , however, the oreshore q tted in vour

f u f a and o deeper water, where no s r bre ks , where the

- o f f a sea bottom is composed so t s nd or silt, a pon derons shell ceases to be essential fo r protective

purposes and becomes a positive. disadvantage in fu lo comotion . This drawback is rther increased in

o f a a a are a as the case G stropod th t c rnivorous, the

are fo r - higher forms mostly , even .the slow moving Bivalves on which they feed requ ire greater activity

ut nd a u a a to seek o a c p t re th n does rooted plant. Hence the reduction in shell an d operculum shown by - the inh abitants o f the lam i n arian as contrasted f with those o the littoral zone . EVOLUTION 105

u The process contin ing as specialization proceeds , the shell ever tends to decrease in size till it remains solely as a protector fo r the m ore vital organs as in

a s P a . . 1 the Tectibr nch ( l te XI I , Figs 4 or dis ap pears as i n the rhipidoglossate Ti ti scani a an d the

N u a P a . s . 0 dibr nchs ( l te XI I , Fig 2 A sim ilar reduction an d disappearance takes p lace

a t am ong the pelagic forms . Light as I n hi na shells are are u a a m a a m s , they s bst nti l co p red to the gl ssy fil — P a . s . 1 2 carried by the Heterop ods ( l te XXVI , Fig 7 2 )

- and s a P s P a X . . 1 hell be ring terop od ( l te XVI , Figs while P hylliri'hoé an d the shell -less Pteropods (Plate — . s 10 1 6 a sca all c XXVI , Fig . ) h ve di rded overing whatsoever .

f a a a a few a The reshw ter G stropod , s ve those th t

ab u u a s a as m c inh it t rb lent w ter , h ve , ight be expe ted ,

s but u Am hi e lea P a . thin shell tho gh p p p ( l te XI I I ,

an d Ph sa P a . . Fig. 5) y ( l te XI I I , Fig 7) tend to over

fl an a u - xam o w their shells, bsol tely shell less e p le rem ain s to be discovered .

a a are a at a s u On l nd he vy shells cert inly di co nt , an d u m u u am u cu a tho gh so e s ch occ r ong the A ri lid e ,

c a s o f Stro hochi lus L eucoclwoa in ert in pecies p , in (where

s s as a a a m a an d it erve p rotection g inst extre e he t), m a o f clo h ridae s a ny the Cy p o till , viewed bro dly, the

c as m c a n d tenden y , ight be expe ted, is to lightening a

m u o f s o f sa a a c di in tion the hell to the p oint di p p e r n e , an d this m ore especially in the carnivorous an d sem i

a u f m . fac a all f m c rnivoro s or s In t , ne rly the a ilies o f 106 THE LIFE OF THE MOLLUSCA

Land Snails culminate with highly specialized rep re

s sent atives, in which the hell is not only extremely

f a - a dwar ed, as in m ny well known inst nces, but is

an al vest i eal a as Chla reduced to intern g pl te, in my

do horus T stacellidae Li m ax P a X . i . p ( e ), ( l te I II , F g and al lied genera (Limacidze) M etostm con (Helicidw) Hy alim ax (Succineidae P) and Athoracophorus or to mere granules as in the Black Slug (Ari on) ; while it wa Tri onochlam s is totally nting in g y , Pseudomilax,

P i lo cus ero i cella n d Oncidi um . h my , V n , a The Scaphopoda have not m aterially altered their

a f and f o f h bits rom the first , the unction the shell is merely to protect the soft parts from the lateral

o f and a pressure the surrounding silt , to th t end the

tubular form is most suited . Among the Pelecypoda the shore -frequenters of

and a a a the older , bro dly spe king , less speci lized types exhibit on the whole stouter an d more convex shells

z E a than the l ater an d m ore speciali ed ones . speci lly

re a a a a stout a some th t h ve, like the Gi nt Cl m ’ B Hi us a (Tridacna) and the ear s Claw ( ppop , Pl te X a f l a of a X I ., Fig . to withst nd the u l be t oce n

re o f f f- waves ; so, too, a those the ossil ree builders o f the R udistes (Plate XIX . , Fig . 7) group. f Nucula la XV The most primitive orm , (P te II a h s f a ae Fig . th t a come down to us rom p l ozoic times is without siphons or byssus but so me species of

a Area P . . an its near lly, ( late XVI I , Figs 5 d which

n a o a a boasts a equ lly l ng ncestry , h ve attained the

108 THE LIFE OF THE M OLLUSCA overlooked because it is situated at the back of the

- broad hinge plate . as B a In proportion , however , the iv lve seeks

o f f a shelter from the strains the shi ting s nd , either

a u in quieter w ters , or by b rrowing deeper, so the shell in response tends to become less heavy and

an a a a solid, d to ssume fl tter shape , permitting o f m ore rapid passage down into the silt . This is seen

a f m u T l a P a o in the later d te or s s ch as el in , s mm bia

' P a . . and Scxobi culai i a. ( l te XV , Fig 7) The h abit o f burrowing deeper is o f necessity accompanied by an increase in the length o f the siphons to insure proper

a and respir tion, this in turn results in the prolonga tion o f the posterior portion o f the test to house

m as a a a f the , well s the ultim te bandonment o the

a f a u fl ttened orm , till fin lly , in the deepest b rrowers,

M idee P a e . . an d a P the y ( l t XV , Fig 4) Solenid e ( late

XX . Fi . 8 f a X , g ) the closed shell is rankly bandoned,

nd a a the v lves, which no longer cover the whole a a fu as f a a a a nim l , nction solely enders g inst l ter l

u f u u press re rom the s rro nding silt . c Fa ility in penetration is , probably, likewise the accou ntable cause o f the elongate shape o f the rock boring representatives o f several fam ilies of Pele cyp o ds . There are a few instances among the Bivalves in which the shell becomes intern al invested by

a : Chlam doconcha w a f the m ntle) y , hich p sses its li e , attached to the sheltered sides o f rocks by its byssus ; EVOLUTION 109

E hi od nta u o f a p pp o , which is com m ensal in the b rrow

o f et a a species Prawn (Axi nus) ; Sci ober i , which is parasite in the ambulacral zones o f an incubating

E Tri E ntovalva chinoderm ( pylus) ; and , which is

a a na p r sitic within Sy pta. No instance o f a shell -less Bivalve has as yet been

. f is n recorded While, there ore, it not so pro ounced s a in the case o f the Gastropoda, there is still evidence o f an increasing tendency in the Pelecypoda towards the reduction o f the shell as one proceeds from . the more primitive to the more specialized f orms . One feature In connection with the Bivalve Shell there is that distinctly shows a tendency to sim plifica and tion , that is the p rogressive reduction o f the m f o h h . f nu ber teeth in t e inge The oldest orms ,

as a o f the P a c c a Neum r such m ny al eo on h o f ay , the m a a f Nu cu a a ore rch ic living orms ( lid e , Arcid e , and the embryo shells o f m any higher form s (Os

t reidae Pt eriidé Philo r i m M ae . , , b y d , ytilid , etc ) exhibit a more or less rectilinear hinge -line with” numerous a sm ll teeth (Taxodont). In the yet more advanced f Cond locardi a an Sci obereti a a orms ( y d ) this st ge ,

m u present in the early e bryo , is s cceeded by the series o f folds (characteristic o f the young stages o f the higher Pelecyp ods) that subs equently divide o ff

an u into cardinal d lateral teeth , th s linking the Taxodont with the Heterodont an d Desmodont types o f hinge . In these last groups the hinge teeth pro n o THE LIFE OF THE MOLLUSCA

res i el um g s v y dwindle in n ber , till in the most

i r h re a a specialized Sep t b anc s they a w nting ltogether, as are a a a a they lso, exception lly, in other less dv nced f orm s Anodonta). In dealing with the Cephalopoda it is essential to

a a u a o f t ke into cco nt the p st history the race, since

a a o f - a f so m ny , especi lly the shell be ring orms, have long been extinct . The modern representatives o f the class number

00 b t o a ut 80 a close on 5 species , elonging bo gener , o f which total about half are referableto the genera " Pol u Se a n d L oli o yp s, pi , a g , while only 5 species (or

all u utilus re less), belonging to the gen s N a , a possessed

f an o external shell .

. Na a a Ca an The utiloide , which beg n in the mbri wi th seven straight - shelled species representing f a u a our gener , attained their maximum in the Sil ri n with about 2 30 species belonging to 20 different

a a genera an d subgenera. Since th t epoch they h ve steadily diminished in numbers down to their

m m d the mini u at the present ay, while surviving

N auti l s a a a a genus, u , only m de its first ppe r nce in

a the Tri s , or in its present limited sense in the

r ff o f Am Tertiary . No did the vigorous o shoot m o n o idea that started in the Devonian an d attained

o f f to a countless host species , which rom some monographs one might almost infer were referable

an to equal nu mber Of genera, succeed in keeping up the number o f testaceous Cephalopoda ; for with

1 1 2 THE LIFE OF THE MOLLUSCA

far C ha So as the shell is concerned , then , the ep lo poda seem to have been yet more eager than the

a an G stropoda to jettison the encumbrance , d their predatory habits have obviouslyhad much to do in

a h stening this consummation .

u f m o f a a f T rning next to the or the nim l itsel , it cannot be said that any definite line o f developm ent

a a o f is presented, unless, perh ps , in the c se the more

a a r speci lized G st opoda, where , with the discarding o f m m the shell , the visceral hu p tends to be s oothed

an d u down distrib ted along the dorsal keel, till the

u u - f tr e sl g like orm is attained . Even this seems to be due to the burrowing habit o f the animal rather

a a u f th n indic tive o f any definite prod ct o development .

u has a a a ante All sion lre dy been m de ( , pp . 33, 34) to the great inequality o f size the anterior and posterior portions o f the body present in certain forms like

M tilus n a ari assu o f y , a d the disappear nce p p the

“ as anterior adductor muscle in proportion , by the increase o f growth in the posterior portion o f the

u n body , it is bro ght more a d more into line with

and u m u and the hinge posterior add ctor scle , con

a sequently ceases to be needful . It is possible th t in the case o f My tilus the predisposing cause m ay be due to the long-continued action o f gravity operating

u a o f u a a on s ccessive gener tions s spended nim ls, aided possibly by som e other m orphological tendency. Whether a sim ilar tendency to m o no myarianism

a f a P ecten Ostrea . observ ble in orms th t like , , etc , rest EVOLUTION 1 13

m a a u a a u on their sides , y be ttrib t ble to like ca se ,

ut at . a m is not clear, b it is le st re arkable that so m any o f the Monom yaria should be form s that

um u f m ass e a position o t o the nor al vertical .

Tridacna a an d c c c , so long puzzle , on erning whi h it was even held that the anim al must have rotated

ha m in its shell , s been shown to be si ply a case o f a Monom yarian that has taken to live with it s um bo

it s a a m ca f a u s c downwards . All n to i l e t re orrespond closely in arrangement an d position with those o f

M ti lus c u a a s y , only it o c pies rel tively reverse p o ition an d it s huge plastic body tends by it s own weight

s a u an d s u f m a s a to pre d o t , con eq ently to or hell th t has it s longer axis in a direction at right angles to l that in the Myti us shell . Am ong other variations induced by environm ent “ ” a o f d arfin c v cas a a s is th t w g, whi h in e ery e p p e r , and a u a so ac a a c f n t r lly , to be tr e ble to the p rev len e o unfavou rable conditions . Thus there is a tendency in Land Snails to becom e

u as a a a u s st nted in size , they tt in to ltit de beyond those in which food is p lentiful an d other co n dit io n s o f life most favourable to them . This is noticeable am ong form s dwelling in high valleys o f

an d - a s the Alps , is observ ble even in tho e on high

i c a m hills in o ur own cou ntry . Indeed it s l i ed that

il r i s 1 00 f a on G t a Head, Tenby, which eet bove sea

v o f H eli x Pi sana are a f an le el , the sp ecimens dw r ed d stunted in comparison with those m em bers o f the 8 1 1 4 THE LIFE OF THE M OLLUSCA noted colony that dwell on the sand -hills just above

- a a m a a high w ter m rk , which is the nor l h bitat o f the

c . a spe ies O n the other h nd, the little black and

a a H eli cella vi x ata white b nded Sn ils ( g ), so com mon

o u r a a over ch lk downs , when they t ke up their abode a sa - ea mong the nd dunes by the s , become dwarfed in their turn . Marine coastal species will also show variation according to the favourable nature or the reverse o f their su rroundings . Marine or freshwater species compelled to live in brackish -water conditions are very liable to dwarfing an d distortion .

a M ni o A n donta r Freshw ter ussels ( U , o ) a e readily aff ua o f su ected by the q lity their rroundings , while Sem per has shown by experiment that the volum e o f water allowed per individual has a very marked effect

m o f Li m n e a sta nali s on speci ens g , the size attained varying directly in proportion to the volume o f water allowed .

' The foot largely modifies in response t o in dividual

u fo r c req irement , whether lo omotory or other pu rpose . The Chitons an d G astropods creep about on the

f m ac o f sole o this uscular organ , the tion which is best studied by observing a Snail crawling on a piece o f glass (Plate The optical effect o f the m otion suggests a rapidly flowing stream proceeding f a a ad an d rom the t il tow rds the he , this is due

1 1 6 THE LIFE OF THE MOLLUSCA an inverted position on the under side of the surface film f o the water .

- a o f a I nthina a XXX . The flo t the oce n roving a (Pl te ,

2 a u o f a a Fig . ) is nother prod ct the ped l gl nds in

ir r e u which a bubbles a e entangl d with the m cus .

a All G stropods , however, do not glide onwards

f Mel u with the steady movement o the Snail . amp s and P edipes have the front portion o f the foot pro podium marked off by a groove across the ventral fa and ce , the animals, when crawling, first advance

n e a f this propodium a d th n dr g the rest a ter it . In the Periwinkle (Li ttori na) an d some of the Po m atiidae = ( a ae f n f lon it udigall , Cyclostom tid ) the oot is t n g y an d the animal walks by lifting and advancing the m alternate halves, like a an with his ankles tied

IL . together (Plate , Fig The propodium is strongly developed and reflected

atica a IL . i aret over the head in N (Pl te , Fig S g us,

0li va Har a and r a f r wa , p , othe s th t o ce their y through ea- and a sand on the s bottom , thus pparently acts

- after the manner o f a snow plough . The expansion

' o f the foot in the Naticidae is assisted by the

f f a re presence o aqui erous sp ces, which a completely separated from the circulatory apparatus. In certain o f the Rhachiglossa and some o f the

a Opisthobranchs, on the other h nd, the margins on either side o f the lower su rface o f the foot (pleuro

a are P 1 6 p odi ) greatly extended ( late 1 Figs . 4, an d and the ani mal is enabled to crawl on the EVOLUTION 1 17

u fa o f s a an d s r ce the loo e s nd without sinking in , to the fin s for f use asg propelling itsel through the mw water ; while in N atazanas these two lobes are united ahgy e the body in such a m anner as to form a m u u a sa O f f c sc l r c p ening to the ront , so that by or ibly expelling the contained water the animal can dart

a b ckwards . “ The wings o f the Sea-Butterflies (Pteropods) are a further modification o f these p leurOp o dia

P . 1 ( late XXVI , Figs . In the Heteropoda the colum ellar m uscle is extended through an d beyond

f and a a a an d a a the true oot , exp nded into l rge l ter lly

m P a . . 0 co pressed fin ( l te XXVI , Fig 2 , f ) , which forms an efficient swimm ing organ as the anim al progresses in an inverted position through the waters o f the open sea. The huge West Indian Fountain Shell (Strom bus)

f u a ff uses its oot in q ite di erent fashion . The pro

um u p odi is q ite distinct, while the latter portion is elongate and bears the claw

a sh ped op erculum at its extrem ity . When the a m a m a a ni l oves , it dv nces these two sections o f its f u m an oot , thr sts the into the silt , d then using them

as a f . nchors, slides the heavy shell orward Other

m P a . . and Stro bs ( l te VII I , Fig 3) their kindred

P tei'ocei'a ' R ostellari a (the Scorpion Shells), , etc progress by bending the foot under the shell an d

a n suddenly straightening it , thus le ping a d rolling over and over . ' 1 1 8 THE LIFE OF THE MOLLUSCA

e etus an d In sedentary Gastropods like V rm , in

a as St l er f an d the p r ite y if , the oot becomes reduced atrophied ; while in the free -swimming Phylliwhoe it no longer exists as a distinct organ .

m a as Nucula The more pri itive Pelecypod , such ,

' and Ti i oni a P a X . . a with its kin , g ( l te XX , Fig 7) h ve a fla f f t under side to the oot with ringed margins,

n that ca be used as a creeping disc . L asswa and

a xiuin P . . Sph ( late XVI I I , Fig though they have

can a no creeping disc, also cr wl on submerged

s an d m o f m fa film object , so e the even on the sur ce

f a . M o f P a o the w ter ost the elecypod , however, an d a a m a o f f f the Sc phopod , ke use the oot to orce a way thro ugh the m ud and silt in which they live . The foot is first extended in the directionin which the anim al wishes to go, the blood is then forced into it so that it swells o ut an d gives some hold w f on the surrounding silt , hen by contraction o the B pedal m uscle the shell is hauled towards it . y a constant repetition o f this process the creature

am slowly advances . The s e method is adopted by

s M a Solen . a a those Bivalve , like y , , etc , th t live he d

. Ensis P a X X . downwards in sand The Solens ( , l te X ,

. 8 f Fig , indeed , owing to the power ul develop m ent o f the foot an d elongate cylindrical shape o f

an d can h - _ eat the body shell, bore down it such gr rapidity that if the animal has been alarmed it is impossible to ove take the diggip . The foot r ' g m” by ”H ' s o f the Cockles not only serves them as a burrowing

1 20 THE LIFE OF THE M OLLUSCA

f e wearer lesgp qn spicuo us in the shadow o v getation . Heli x desertaram The dun colou r o f the Desert Snail ( ),

a f a a like th t o the other desert anim ls , h rmonizes with

a the prevailing tint o f the habitat . The rboreal A ri ophanta D ohertyi o f Sum atra is o f a delicate green

u an d a a s f a colo r , lmost invisible mong t the oli ge on c M f whi h it dwells . any o the Slugs , by their colour

an d m a are ing rkings , rendered inconspicuous in

a a u u their n tur l s rro ndings , such as Li m ax arboxuin

eo al s K on trees, G m acu (the erry Slug) on lichen covered rocks . Certain o f the Philippine genus H eli oostyla carry colou r protection to a higher stage

- a when dry their grey brown periostr cum , which is f o f air a a f ull sp ces , m tches in colour the dead oliage o f the forests where these Snails have their abode ;

s r f m when the heavy howers, which a e requent, i part a a a a air a rich d rk colour to the de d le ves , these sp ces ar m n u e filled up by the oisture, a d their periostrac m then allows the u nderlying dark colou r o f the true

a m test to show through , so th t the shell once ore harmonizes with its surroundings . On drying again f it speedily resumes its ormer hue . The reason fo r the co loration on some shells — Cones, fo r instance that are covered during life

a a u n t read l e. with thick periostr c m is g , i y exp licabl

Ma o f m a r ny the rine shells , however, that a e not

are thus invested, so marked as to be inconspicuous in their proper habitat ; while others are coloured a to m tch the objects o n which they live or prey . EVOLUTION 1 2 1

Thus Ovula and P ediculai'i a are yellow or red accord ing to the colour o f the corals on which they occur . The phenom enon is comm on enough am ong the

c o f H erm a n den Nudibranchs . Green spe imens dr i a a it c confine them selves to green seaweeds , where s

H bi a f . Auchi the red . fid is ou nd only on red weeds dori s flam m ea closely assim ilates in hue the bright a red sponges on which it feeds . Endless simil r

s a c are fa aff . in t n es , in ct , orded by this group Pelagic species o f Mollusca are generally trans

a an d c u s u s u . p rent olo rle s , nle s tinged with bl e

P a rotective coloration is , however, c rried to its greatest p erfection in the Dibranchiate Cuttl efishes. Scattered over the skin o f these anim als are pigm ent cells containing different colours which becom e visible on the exp ansion o f the cell by the muscle fflmes with which each is furnished. Their control

c c isual v an d is onne ted with the y ner es, by reflex

r u u action they a e bro ght into play, so that the creat re is able m ore or less voluntarily to adapt the colour o f its body to its im m ediate surroundings after the

more fam iliar example o f the Chamaeleon.

M f u a ore req ently, perh ps , protection is as it were adventitiously afforded by the shell becoming coated

over with extrane ous matt er . Many o f the land

a am f shells , especi lly those living ong the roots o

a m a a . pl nts, tend to beco e co ted over with e rth

Li m neea runcatul a c a t , whi h delights to cr wl out o f

a a a w ter on wet mud, is usu lly so co ted over as to 1 2 2 THE LIFE OF T HE M OLLUSCA resem ble a s mall m ass o f that substance . The shells o f the true Water Snails are often quite over

m an d ar grown with inute green weed, so , too, e those o f marine G astrop ods . The latter , moreover, are frequently encrusted with calcareous Algae (Nuli

m a pores , or overgrown with so e Hydr ctinian till they are unrecognizable . A more curious and

ff u Xeno hor striking instance is o ered by the gen s p a, the m embers o f which build on to the upper surface o f a at a f the shell , especi lly its m rgin , ragments of

a — a fa stone , cor l , or other shells wh tever, in ct , is

m m sea-flo o r a co on on the where they h ppen to be, after the well -known manner o f the Caddis-worm

P . . ( late XXVI I I , Fig Among the Bivalves some species o f Lim a and Volsella M odi olus) attach various bits o f marine refu se to themselves by threads o f the byssus till

m . Li i an they are ore or less concealed thereby m a h s,

a u a o f . indeed , is credited with reg l r nest this sort Of other forms o f protection o f a more active nature m ay be m entioned the possible advantage of spiny shells in preventing the occupant from being swallowed fo r food : the poisonous bite o f the Cones

m s ay likewise erve in good stead .

a f It is mong the more de enceless Opisthobranchs ,

a a a far however , th t the best inst nces h ve so been met

with . Oscanius is known to secrete an acid from the

fa o f . A ncula D ata an o f sur ce the body , , d many the

A 1 2 4 THE LIFE OF THE M OLLUSC

- S u a well as the sponges , needle like pic les which m ke them u ndesirable as articles o f food ; hence the im portance o f the mim icry . How far one mollu sc devoi d o f special self-defence m ay mimic another kind furnished with some de ha fensive protection is a moot point . It s been

o f Stxom bus suggested th at a cert ain species , the

a o f a Conus m a shape o f whose shell resembles th t , y derive some advantage thereby in view o f the poisonou s bite o f the latter . There seems more probability in the case o f two Philippine Land Snails— H eli cai’i on tigif i nus an d Xesta

Cu in ii— o f a a m g both possessed sm ll thin shell , into an d a a a which the animal cannot retire, rem rk bly “ - a f long, narrow, high ridged t il to the oot, which form s the most likely looking hand-hold fo r their

l ' captu re . When so seized the He icai i on parts with

a an d a Xesta a its t il esc pes , while the is un ble to do

an d a a so , it is thought that birds cqu inted with the futility o f attempting to capture the one would leave the other in peace also . The alimentary system in its entirety does not

f a o f l a a present e tures evo ution ry interest , lthough m inor variations in response to individual require

r um f ments a e n erous . O these the mos t interesting

' is the development in the gizzard o f the Bullidae o f

a a a a I. n c lc reous pl tes ( Pl te I I , Figs . 9 a d whose f a re unction is to crush the sm ll shellfish , which a swallowed entire . EVOLUTION 12 5

1 The radula (Plate II I . , Figs . 1 which is

f u characteristic o the phyl m , exhibits consistent pro g gess as one passes from the lower to the higher u fa a Rhi ido gro ps . In the older milies , especi lly the p o i sa are a ; gl , the teeth we k , but numerous indeed, there m ay be as many as 300 or more in each trans a c o f u verse row. The most arch i member the gro p ,

Pleur t ri a m m an d o oma , shows the ost pri itive type indicates that it has been derived from an earlier

ll a a one, in which a the teeth in tr nsverse row were

a . o P leurotom ari a an d m simil r N w, in the more pri i

a a tive Rhipidogloss , three longitudin l tracts on either

f a are a side o the medi n tooth distinguish ble , but in the higher members o f this division it is found that the several teeth in one tract are replaced by a single

a a a f ac o f l rge one , which gener lly ret ins su ficient tr es the individuals it replaces to suggest that it rept e

f m a c u sents the fusion o a series . Si il r cases also o c r in fu molluscs yet higher in the scale . This sion ,

l a u a extending to al the tr cts, res lts in the taeniogloss te a f 1 1 1 r dula, whose ormula is 1 1 1 1 (or

1 1 1 P . . fu 2 2 , late I II , Fig By rther f a a usion , or , r ther, s would seem to be more probably

a a o f o f a a the c se , by the bortion the outer rows l ter ls , is derived the type o f radula met with in the Rhachi

a and o f a gloss more primitive the Toxogloss , whose

f u a 1 1 1 P a . . Har er orm l is ( l te I II , Fig In p ,

Mar i el a n u a . 1 g n l , a d the Vol tid e ( Plate I I I Fig 8) f the process is carried a step urther, and only the 1 2 6 THE LIFE OF THE M OLLUSCA

a . median tooth is left . In the Cones (Pl te I I I , a Fig . on the other hand , it is the medi n row

a a a a u o f a th t dis ppe rs , le ving the do ble row b rbed

a a Of o f l ter ls . course this line development is not

u a o f a exemplified in all . N merous c ses pparent exception occu r am ong fam ilies that lie o ff the m ain

a a a br nch , or th t in this respect ret in archaic charac

. u are E i ton um P a . . I ters S ch p i ( l te I II , Fig an

thina . , etc The Opisthobranchia offer every variety o f radula in their ranks from the uniform multiserial to the

o f E l si a an m c single row median teeth in y , d u h fu rther research will be necessary ere a solution o f this diversity is found .

P m a a a o ff e n d The ul on t br nched arly , a have

a a f o f a a u m o difica ret ined primitive orm r dul , s ch as are a 11 1m tions there being princip lly in the 1. . an d fo rm o f ua , lggtb the cu s on the_ individ c i s l , p

P a . . a ( l te I I I , Fig These modific tions proceed f m m a n a a an ro the edi n li e outw rds , so th t inspection o f m a a o f the rgin l teeth , or those the embryo , gives a clu e in. many cases to the ancestral radula. Only

P oli ta an a a m one genus , , shows ppreci ble di inution

u f f r a in the n mber o teeth , o where s the Common Garden Snail (Heli x aspersa) has about fifty- five teeth on either side o f the m edian in each transverse

P oli ta row , this number is reduced in to at times as few as twel ve .

a a P . The higher Ceph lopod ( late I I I , Fig . 20) h ave

1 28 THE LIFE OF THE MOLLUSCA as the right (originally left) ctenidium becomes a an d a a aborted in the higher Rhipidogloss , dis ppe rs

as o f a o f in the rest, the EQSJm the gener l torsion the a d1m 1n i shes an d body , so the corresponding uricle

f a disappears also . The simplification o the he rt in

a f due an this c se, there ore, is not to y progressive f development from a less to a more per ect condition . The respiratory system supplies some very ill ""

esti n o i n t s . a a g _p There is every indic tion th t the primitive gill o f the Mollusca must have co nsisted o f at a a a o f ve sim le - s uc u le st p ir p plume like tr t res , ry‘ an d th at as increased facilities fo r respiration were

o f u s m c a f required, which, co r e , i plied in re se o gill

fa a f sur ce , it could only be obt ined in one o two ways the flattening o ut into a leaf-like expansion o f

ua i -filam en t s as ido bran ch individ l g ll ( p ), or their f o n gatio n (pectinibranch). The ormer m o difica tion is the one that appears in all the archaic

f ff a and m a members o the di erent cl sses , y be recog

P a a n iz ed in the olypl cophor , the rhipidoglossate

a a a nd Gastropoda, the protobr nchi te Pelecypod , a in

u u the Cephalopoda. This str ct re, nevertheless, is

a o f a a limited by the confined sp ce the p lli l cavity, an d further increase o f surface can only be gained

- by the corru gation o f the gill filam en t . A beginning o f such pliCatio n is observable in the case o f P leura tom axi a an d u e A , do btl ss it exists in other spido branchs as well ; but it is carried to a much greater

in a - l degree the Cephalopod , in which the gill fi a EVOLUTION 1 2 9 ments exhibit two series o f plications crossing one another . In the Gastropoda the progressive atrophy an d disappearance o f the right (originally left) ctenidium as one ascends from lower to higher members has

ante . a already been alluded to ( , p The initi l

P leurotom ari a but far stage o f this is shown in , it is

a m ore marked in Sci ssurella. In the Pectinibranchi

has um a a bu t not only "one ctenidi dis ppe red, the other (except in the case o f Valvata) has becom e attached by its whole length to the wall o f the

a a c and as a u has a p lli l avity, conseq ence p rted with o f row f am ents on a SO the whole the w o fil th t s ide ; that three -quarters o f the gill - potentiality o f the

i B f a a p rimitive mollusc s sacrificed. y way o p rti l compensation the individual gill-filam en ts have been som ewhat lengthened till the fam iliar pectinibranch

c a s . I anthi na P . . ondition ri es In ( late XXX , Fig 2)

-filam en re fu m these gill t s a rther ore plicated . The com p licated m odifications that take p lace in the gills o f the Pelecypodahave already been described

an te . 8 n d s c ( , p p 2 a in e the classification o f the

u is a and gro p b sed thereon , need not be redescribed . Many kinds o f aquatic m olluscs have lost their

s a an d a s gill ltogether, in these c se the respiratory fu c a u m n tion is t ken p by the antle . This is the

a m m L P a . c se with the Co on impet ( l te IX , Fig . “ ” the circle o f gills su rrounding the edge o f the mantle just under the shell are outgrowths o f the 9 130 THE LIFE OF THE MOLLUSCA

“ - f a f a . o o m ntle So , too, are the plume like gills m ny

f P . . 20 o the Nudibranchs ( late XI I , Fig but in others o f this group those curious o utgrowths known ” as a a l u fa cer ta, as well s the general mant e s r ce, also take on the function o f respiratory organs . In the terrestrial Snails and freshwater Pulmonates respiration is carried on by means o f the complex network o f blood-vessels that overspread the roof o f “ ” t he a a . p lli l cavity , which thus acts as a lung In one family o f marsh frequenting Snails (Ampul a ae al ch m ber t o l riid ) the palli g is divided into w, - a a a f the rig ht h nd cont ining gill , while the le t is a g l m o n ar ha converted into p y c mber, whose opening is transformed into an extrusible sipho n which the animal uses if near the surface o f the water ; or it can breathe by its gill under water and by its lung

o f a a IL . when out w ter (Pl te , Fig All these chan ges appear to be made in response h to the demands of the environment, even the hig ly com plicated structure evolved in the Pelecypoda is a question o f the requirements o f respiration solely. The m ajority o f the gill -bearing Gastropoda and the less Specialized Pelecypoda live in wat ers that are

tan a o f a and cons tly in state more or less agit tion ,

a where, consequently, ent ngled oxygen is compara t ively abu ndant ; whereas the Bivalves that burrow do not get the water in their lurking-places so ful ly

f ae n or so requently rated , a d hence the necessity fo r being able to extract proportionately more oxygen

132 THE LIFE OF THE MOLLUSCA

and a Mollusca is limited . The Cephalopods G stro pods afford instances o f progressive development in

N auti lus n d h this organ . In a in t e Limpet the eyes are simple pigmented info ldin gs o f the integument

n f a a XX X. . 1 2 without a y re r ctive body (Pl te I , Fig , C). A crystalline lens is present in the more archaic

a a an d f rhipidogloss te G stropods, in the rest o the G astropoda this is enclosed by a cornea (Plate — X X . . 1 2 B . a n X I , Fig , ) A corne i complete in the '

i o ida a . . 1 2 A O g p s (Pl te XXIX , Fig , ), but complete — ’ in the Myop sida is also present in the dibranchiate a a Ceph lopod , while the Octopus , in addition , p os sesses an eyelid . In those cases in which the eye becomes buried in the integuments , or the animal

a a a a is abyss l or subterr ne n in h bitat, this organ a r a Natici tends to become rudiment ry (ce t in da , Bul a Pleuro branchida an d lid , the , some Pulmonates) or a r o f a to be wholly w nting (sund y species N tica, b a o f Olivida Bulli a Tere r , the , , some subterranean

a a a al a Pulmon tes, cert in byss G stropods, internal

E nt oco nchida an parasites like the , d pelagic forms

nthi na an d such as Ia the Pteropods). a e Among the Biv lves , xcept the Mytilida an d

Pteri a t e lic are a in a u , g ew c p ha eyes w nt g in the d lt, though present in some larva . Accessory eyes are developed in some molluscs in other parts o f the body. In certain species o f Chiton s a are a c ttered over the shell m ny thousands o f eyes , some with and some without crystalline lenses they EVOLUTION 133 are ranged in rows running from the front beak o f m each shelly plate diagonally to its outer edge . So e

’ z i a species o f the pulmonate Onc d um have , in ddition

a a um o f to the eyes on the tentacles, l rge n ber

Others situated on tubercles over the back . These particular Slugs are said only to be found in the mangrove swamps where the peculiar fish P eri o

htkalm us a n a n p bounds, hoppi g lo g the shore in

f n d has u a search o prey, a it been s ggested th t there m ay be som e connection between these two occur

e but has . ren es , nothing very definite been decided In certain o f the Pelecypoda accessory eyes are found on the edges o f the m antle an d at the extrem are co m ities o f the sip hons . In the Arcidm there pound eyes to the num ber o f more than two hundred

a a m . c en P a . pl ced long the mantle argin P e t ( l te XV ,

. 8 an d S ond lus a a as a but Fig ) p y h ve ne rly m ny , they are a an a m isol ted d borne each on a short tent cle , ore

f a o f f u a being ound on the m rgin the le t , or pper , th n

a o f m a . on th t the right , or lower , ntle lobe The

' structure o f these accessory eyes in Onczdi um an d the Pect enacea resem bles the vertebrate eye in that the visual rods are turned awa from the li ht . y _ _ g L Vi ua a but a ua s ess complex s l org ns , ne rly eq lly sen i

are f m a m a Of tive to light , ound in the ntle rgin

'

Osm a P tem a P i na n Mactm . a s at , , n , a d The tent cle

/ o f s o f Can diam P a . the ends the ip hons ( l te XXIX ,

I Li tho om us Pholas M a E nsis an d s Fig . 3 ), d , , y , , other , bear eyes that are more or less sensitive to light an d 1 34 THE LIFE OF THE MOLLUSCA

a an a o f the a a sh de , d so w rn their possessors ppro ch f o possible danger . With all this capacity fo r ready response to the a i o f a ct on environment , it is little wonder th t members o f widely different families and even orders , f subjected to similar conditions o existence , should com e to bear striking resem blance to one ano ther . To the recurrence o f the Limpet-shaped shell and

he f - f a has t repetition o the Slug like orm , llusion

al ea ante . 1 an Ma r dy been made ( , pp 03 d ny other similar instances occur among Gastropods,

a S co ’ s a not bly y bpu (Rhipidogloss ), which resembles

Fi cus T ni lo a a XX . 1 1 an d ( a og ss ) Pl te X I I , Figs .

an Strombas Mauri ti anus a d (Taeniogloss ),

a Conus anas a simul ting j (Toxogloss ), while there are equally noteworthy examples among the

’

P a. oralho ha a a s o f a elecypod C p g , genu Cyprinid e in its external appearance

Li thodom us n f M t ilidw closely resembles , o e o the y

a a a . 1 and (Filibr nchi ) (Pl te XXXI I , Figs. 7 whose

ante . Dre ssensia burrows it occupies ( , p i , the f a M Su reshw ter Zebra ussel , belonging to the b

a a E a a a a m is mytil ce ( ul mellibr nchi ), is const ntly placed o u account o f its striking similarity to Septzfer

M P XX . with the ytilacea (Filibranchia) ( late XII , 1 Figs . 3 and A a , nother noteworthy inst nce is ' a aff P etri cola haladz r is th t orded by p f o m , one o f the

ae u Venerid , recently introd ced into this country, eem f A a s ingly with Oysters rom meric , that at first

1 36 THE LIFE OF THE MOLLUSCA

’ reco rds finding a species o f Heli cam on (already “ 1 ante .. a a alluded to , , p 24) th t shed the t il when touched by whisking it up an d down till it became if se “ detached, or ized by the tail the animal dropped off and escaped . CHAPTER VI I I

INSTINCT , IN TELLIGENCE, AND USES

NSTINCT an d intelligence as we u nderstand them are hardly qualities that one would look fo r

ho m in in ti n ct in molluscs, nevertheless the g s is dis m

a m t a . L pl yed ‘ by ore h n one The impet is well known to return after each graz ing excu rs ion to the selfsame spot on the rocks to which it has fitted it s

m m a a an d shell . The Co on G rden Sn il the Slugs punctually return after each nocturnal ram ble to the

c a a a a has m a nook or orner, cr ck or cr nny th t e ch de

o f n its hom e . A somewhat higher order intellige ce is that cited by Darwin on the authority o f

H eli x Mr. L a a a onsdale, in which Rom n Sn il ( pom ati a) m ade its way from an ill -stocked garden

a - f an d over the wall to one rich in pl nt li e , returning , f m a etched a weakly co p nion , which it piloted to the land o f plenty it had discovered . Madame Power declares that she once saw an Octopus in her aquarium watch a P i nna till the shell Was well open an d then deliberately pl ace a fragm ent 137 1 38 THE LIFE OF THE MOLLUSCA o f a rock, which it held ready, between the v lves to

a prevent them closing , when it e sily devoured its f w de enceless victim . The same animal as also seen to watch by the side o f a big G astropod till the latter f emerged rom its shell , when the Octopus pounced on it . The uses to which Mollusca and their shells both

a an d r h ve been a e put seem almost endless . Primarily they have served from prehistoric times as a f o f M rticles o diet . The shells Oysters , ussels,

n Cockles, Periwinkles, a d other edible kinds , mixed with bones o f beasts an d birds that had shared their fa are f r - te, ound in the efuse mounds known as

1 0 kitchen middens , which range from 0 to

f an d f m 10 f i and eet in length , ro 3 to eet h gh ,

n d r which occur along the coasts o f Denm ark , a a e even represented by small deposits in places in these

- islands . Later date counterparts o f these refuse

a are N a f he ps met with in orth Americ , ormed

a o f f enus m ercenari princip lly the valves o V a, in

B az a r il , Tierr del Fuego, Australia, New Zealand,

etc . In caverns in Liguria enormous accumulations f L o impet shells tell a like dietary tale . To -day nearly all the marine Bivalves are eaten in

u f one q arter o the world or another, as well as many

f m a n e o the arine G stropods a d ev n Chitons . Cuttle

are a a fish esteemed in It ly, Provence, Spain , Chin ,

a a and Ea a . J p n , the st gener lly

f s a a r The re hw ter molluscs , being less t sty , a e not

140 THE LIFE OF THE MOLLUSCA

’ a an d in the Pharmacopoeia from Pliny s d ys , down to quite recent times there has been a widely prevalent belief that they were especially efficacious as a remedy fo r consumption .

a u a After food comes ornament . In v rio s c verns o f the Stone Age in Southern France nu mbers o f littoral shells bored fo r the purpose o f threading

a n f as as f a h ve bee ound, well ossil shells simil rly

- a all a o f treated . Present day s vages in p rts the world utilize them fo r personal adornment in many

a an w ys , sometimes simply boring d stringing them , sometim es preparing portions only by rubbing

u down till the req ired part is left . Specially prized kinds are either em ployed fo r particular forms o f ornament or are reserved fo r the exclusive use o f

f f n f chie s . Sections o big Top Shells a d Cones orm

a are a and u a ing l rge rings prep red sed as br celets , an d recently were imported in quantities as armlets

r f fo ladies to keep up the long gloves then in ashion .

fo r a Their other modern uses orn mental purposes ,

are an d a — f m ash as well known , extensive v ried ro

a M - o f - a a tr ys to other Pe rl inl ying work , while

a f an a a a a an d a pe rls orm ddition l item p rt , h ve been

ar highly esteemed from very early times . These e obtained not only from the Pearl Oyster o f Ceylon

n E a are f a d the st , but met with in the reshwater Pearl

Mu Mar ari tana m ar ri t er an d ssel ( g ga if ), their fishing once fo r-med a valuable industry ; while the occur rence o f pearls i n the Zebra Mussel (Dreissensi a) in N N N ELL EN E AND U E 1 1 I STI CT, I T IG C , S S 4

ff ha . m a s Sta ordshire s been recorded Indeed, the Ro n seem to have held the British freshwater Pearls in

P Cm sar high estimation ; while , according to liny ,

u an d u dedicated to Ven s Genetrix , h ng in her

m m a a a B te ple at Ro e, bre stpl te covered with ritish

u s f m m a pearls, tho gh the e were possibly ro the rine

M c as as s m m s ussel , whi h , well the Oy ter, so eti es yield

f , a f m pearls . A large dull kind o pearl is lso got ro

Tuidacna a am an d P a s f m (the Gi nt Cl ), p ink e rl ro

tif o bus i as as the West Indian Fountain Shell (S m g g ),

' a s o f well as from certain Tui binella. Fossil pe rl

a m f u o ur E l rge size have , oreover, been o nd in nglish

f B a Ino chalk, being the product o the big iv lve (

ce u Dr. was m m s) that occurs therein . Willey fortunate enough to obtain a large pearl from a

N utilus s B a a a hell in New rit in, this being pparently the only one known .

a a u a a u For pr ctic l tilit ri n p rposes , however , the

u m f So th Sea islanders m ake the ost use o shells . They employ them as sinkers fo r their fishing nets

m a as a fo r u s m a ufa u in so e c ses b it C ttlefi h , n ct re

fish- an d a s o ut o f hooks , weapons , even sh ving tool them . In China and J apan the translucent shells Of

a u fo r an d is P lacuna placent are sed windows , there

- a a a Window Shell Oyster fishery ne r Trincom lee,

Ceylon . The silky byssus o f P inna has been woven into

. and a a u gloves , caps , stockings , etc , T r nto, in So th 1 4 2 THE LIFE OF THE MOLLUSCA

a w f u a It ly , as the headquarters o this q ond m industry . In som e quarters o f the globe shells serve the

u f f ' p rpose o money . O these the best known is the

M rwa m oneta u oney Cowry (Cyp ), which sed to pass fo r a an d a currency in Indi , is still l rgely used in

f o f N - West A rica. Among the tribes orth Western America a species o f Dentalium was employed till

‘ u n f s perseded by blankets . O the eastern coast o ” N m a m was m u orth A erica, w mpu long the edi m o f exchange : it was form ed o f beads made by grind

e c ' ing down the Common Clam ( Venus m r enai i a).

f m f am m a f Saxidom us Another or o w pum , de rom

‘ l ti a u a f a an d H a i o s, w s c rrent in C li orni , while in Benguella the same sort o f money was manufactured

’ out o f a Lan d Sn ail (Achatina m onetai i a).

B a - In New ritain the n tive shell money, or ” f f assa callosa a diwara, consists o shells o N , ble ched,

o ff and perforated by knocking the curious hump, threading them on rattan slips .

- a - Besides these there is the shell be d money, gener ” a o f Ma a a ally known s rongo , l it , in the Solomon

o f u — and Islands , which is three colo rs white , red,

a f m Area ranosa black . The white is m de ro g , the

f m ha a P ac ca an a f a a red ro C m ifi , d the bl ck rom bl ck

Pi na. Mussel , or n More quaint was the custom prevalent at one time

o f a on the west coast Scotland , whereby , when

u f a - f bargain was str ck , each o the p rties kep t one hal

1 44 THE LIFE OF THE MOLLUSCA frequently the cause o f poisoning when eaten .

Li m naea t ca a a s a ante . run tul , as alre dy t ted ( , p is the intermediate host o f the Liver Fluke o f Sheep . The m ischief that Slugs an d Snails can work to crops an d in gardens is only too well known ; the former are also said to dam age Co rks . The amount o f mischief that has been caused by

- Teredo m a a the Ship worm ( ) is al ost inc lcul ble, but with the passing o f the wooden ship and the ex

use f and fo r tensive o iron steel work piers , its destructive energies are now mainly confined to

- the timber work o f groynes and landing stages . f There it is still the despair o the engineer, fo r no known method o f treating the piles will keep the foe at bay. The prices paid by collectors fo r fine specimens of

a s r re shells , although at one time con idered high, are insignificant beside those given o f late years fo r

u 10 . a scarce postage stamps . Th s £43 5 was p id in

1 8 fo r a Conus lori am aris an d 186 fo r 54 g , £42 in 5

“ was a a another example . The latter figure lso re lized

f a fo r a o f C i wa uttata the ollowing ye r specimen yp g ,

an d 0 fo r a C. rince s as u as 100 £4 p p , while m ch £ is said to have been given fo r a single specim en o f the

arinari a heteropod C , now worth only from 5 to f m £10. O late years the highest su paid for a single shell was that given fo r the magnificent P leurotomaria

Adansoni ana Na a H , now in the tur l istory Museum, fo r a a which the origin l vendor obt ined £55 . IN DEX

” J R eferen ces to the Plates are given in rom an num erals.

A SS M o llusca Am ki e lea 10 BY AL , 5 5 p p p , 5 Aeanthi na 6 Am hi e l i ea lut nosa iii . , 9 p p p g , x Acanthina i m bricata xi Am ullari a 60 , . p , 47 , , 75 Acanthocem s Rhotom a ense xxn Am ull aui a canalicul ata u g , . p , . Acanthoehi tes 1 02 Am ullari a lobosa , p g , x . Aeantho leura s inosus ix Am ull arii ae 1 0 p p , . p d , 5 8, 3

A oavus ham astom a v . Am ullina si aretina . , p g , x Ace hal a 26 Anadenus 60 p , , A bullata xii A ccra . nati na subrostrata . , , xx A ehatina 8 o An ati n acea 8 , 7 , g , 7

Achatina achatin a iii . An c lidae 8 , x y , 5 Achati na m onetaria 1 2 Ane loeeuas s i ni erum i i , 4 y p g , xx . Achatinella 6 Anc lus F reshwater im et , 4 y ( L p ) , 5 3 , Aciculidae 60 8 6 8 0 I 0 , 5 , 5 . 5 . 9 , 3

Aem e a testudi nali s i x . Am lus uvi atilis iii , y fl , x . Aeroloxus 10 Anim al s eedin o n M o ll usca , 3 f g , Arman touna ilis x11 — t , . 76 7 8 Acula 1 22 An nul 8 , us , 3 Adducto r m uscle su ressi on o f Anodonta 2 1 10 1 1 , p p , 5 , 5 3 , 74 , 9 , , 4 , n teri r a o , 33 13 1 Adductor m uscles 1 Anodonta Em r o i , 3 , b y , xx x . Adm ete 6 Anodonta c naa w n M ussel , 3 yg (S a ), E i res uncti lucens I o 8 g p , 74 . 9 B olts 1 1 Anomi a 8 , , 4 iEstivatio n Anemi a t es i n rowth , 73 , S ag g , 95 , E theriidm 8 i , 5 xx x . Air i n ch m ered Ce h lo o d An m a A chum s xvu a b p a p o i , . hel l o S , 39 An stom a, 98

All o ri sm a 6 Anostom a lobul osum II . i i i . , 4 g , V I , x A e hi h M l sc are i n l 0 ltitud s at w c o lu a An ter o r ca a , 2 o un d 60 A ert ure o f Shell 1 f , 5 9 . p , 9

Am ber Sn ail s See Succinea. A e 1 , p x , 9 A i l 10 A l co ho ra 1 1 12 m ou a, 2 p a p , 4 , 5 , 7 Am m nites A leeta h norum o , 99 f yp , 5 9

Am m o noidea 1 A l astrum a lustre xu . , 39 , 4 p p , Am hibola 2 6 A l si a Sea Hare 2 1 p , 5 , 9 p y ( ), 5 , 5 5 . 43 - i i a ii Am hibola ni i x avellana v . A l si a de l ns x . p , xx p y p , Am hineura 1 1 8 88 A l siidae 2 p , 4 , 5 , 7 , p y , 5 10 146 THE LIFE OF THE M OLLUSCA

oremodon 10 Baso m m ato hora 2 Ap , 53 , 3 p , 5 A orrhais B ath dori s ab ssorum 6 p , 97 y y , 5 ’ A orrhais as- el ean i i Be r s Cl ee Hi o us p p p e i , . a aw. S pp p . A rea Ark Shell s 2 8 10 Bela 6 ( ), 3 , 34 , 4 , 6 , 3

A uca uanosa 1 2 Belem nitella m ucronata xxv . g , 4 , Area N ow vii Belem n ites 6 2 , x . . 3 , 4 , 49 A f ca vi vi ara 2 B elem ni tes 0 p , 9 , 4 A rea z ebra vii B elemnites resto re x i I , x . d, . bi ari na us xxi B elem noteuthi s i A seestes e t . 2 v , , 4 , xx . A rchanodon ukesi i 6 B elero hon 2 0 j , 4 p ,

A rchidori s 0 B elero hon bieari natus vn . , 9 p , A rehidori s ammea 12 1 B elo tera belemn toides xxv fl , p i , .

Archi teetoni ea ers ecti vum . B elose i a i v p p , VII p , xx . ’ Arcidae 10 1 Belose za se ioidea xxv , 9, 33 p p , . Ark Shells See Area Bel oteuthis 1 1 1 . . , 49 , Ar onauta Pa er Nautil us 0 Bi th ni a g ( p ), 4 , y , 5 3

6 1 0 88 1 Bl k lu . ee Arion . , 7 , , 9 ac S g S

A r onauta ar o xxi . Bl aos i ra echinus 8 ii . g g , p , 9 , xxx Ar uta i ans xxv Bli t r Pe l ona h . s e ar s g , , 5 A ri on 1 0 h ll r ana 8 , 6 B rac ypode a B ooksi , 9 , A D h r XX“ riophanta o e tyi , 12 0 X . A i i Mo lluscs i i o hanta le ui es ii . Brack sh Water p p , x , 57 Arm s o f Ce halo o ds Brechites ater- o t Shell 2 p p , 35 (W p ), 3 . A l 1 sco g o ssa, 2 33

As ido branch : Fo liate Gill iii . B rechi tes va ini erus . p , g f , xx As ido bran chia 2 Brownia p , 4 , 93 ' A ssemania B uccznum Whelk 12 2 , 5 7 ( ), , 4, 55 , Astarte 6 88 6 68 8 , 3 , 3 , , 9 ‘ i cinu unda um C m m o n Astar e sulcata v ii . Buc m t o t . x (

A horaeo rus 106 helk ii . t pho , W ), 55 , - A tlanta Peroni x vi . Bucci num undatum E ca sules , . , xx , gg p ,

A traeti tes 8 . , 4 xxx ‘

A tari a zi cz ac ii . B ueci num undatum radula i n . , xx ,

A s naucum y . Bull a 2 ty , , 5

u er hells . See Terebra Bulla am ulla xu . g S . p , Aula ceras 8 1 1 1 B ulli a 1 2 eo , 4 , , 3 Auri ula 2 1 Bulli ae 1 2 e , d , 3 cula ud iii Bullin ella 1 1 1 Auri a . j . x , li ae 0 B ulli nella c lindrat ea xi i Auricu d , 5 3, 6 , 96 y , . ' ri a Burr win Biv lves m etho of A vi cula Pte o g . a d 1 18

Baculites ance s i i . B ursa lam as vi . p , xx p , B alea 8 B ssus 0 , 9 y , 3

B alea erversa iii . B thini a=Bith nia. p , x y y

B anki vi a varians , i x. i h h l Bargai n s struck w t s ells, 142 Ceci i oides . 60 B arnea 1 Caeum 2 1 , 35 ,

B arnea Bakeri . Caeum im er aratum , xx p f ,

B arnea candida ii. Oalcarelta , xxx , 93

148 THE LIFE OF THE MOLLUSCA

rt Conus ponderosas, vu . Cy odari a, 63 Conus tesselatus ii C rtodonta , v . y , 45

Co hinoceras Ei elense i i . C rtolites p f , xx y , 45 oralli o ha a 81 1 C p g , 5 4, , 34

Corallio ha a coral li o ha a i i . Daudebardia brevi es iii p g p g , xxx p , x . oralli o hil a 81 Dawsonella C p , , 47

Corbi eular onsobrina viii . Deca o da 2 , x p . 4 C rbula sulcata x Del hi nula laci ni at i o , xi . p a, x . orburell a Dendronotus rondosus 12 x C , 49 f , 3 , u.

osm oceras s ino sum xxi I . Dendro u a C p , p p , 47 ’ ’ Co wr . ee C r a Den tal iidae El h T y S yp a . ( ep ant s usk ' Cras edoehzlus ci nereus Em r o Shells 10 26 p , b y , ), ,

i . Dentalium 26 1 2 xx x , , 47, 55 , 95 , 4 l D ntali rassatel a 6 e mn stru ture of xv . C , 4 . c ,

Crassatella ulehra viii . Dentalium ele han ti num xv p , x p , . r n cone us Dentali um le l C em o h , 5 9 ptaske es, 56

Crests aei eula vi . Dent lium Tarentinmn Em r o , xx a , b y ,

Crioceras 8 i . , 3 xx x Cri oceras cristatum xxu Des oenidae 60 , . p , Cr toehi ton 102 Develo m ent of Em r o 2 yp . p b y , 9 Cr to l ax 102 De tral shells I 8 yp p , x ,

r to laz : radula iii . Di a hora tuba 8 C yp p , p , 9

Cr ta lax larva orm i s i x. Di ran chia 0 2 12 1 2 yp p f , b , 4 , 4 , 7, 3 Ctenidium Dibranchiate Ce hal o o shells , 7 p p d no do n ta co m ared xx iv Cte , 45 p , .

u idaria cus idata . Di m aria C sp p , xx y , 34 i ariidae Di saeeus s irat s xi Cusp d , 35 p p , . uvi eria 6 1 Diseases caus d b M oll usca C , y .

ieri a columnella vi . I Cuv , xx 43

n m a Dis ersal o f M o ll usca 8 et se . Cyclo e , 45 p , 3 qq clo ho ridae 60 Distri ution 1 Cy p , , 73 b , 5 “ C o horus i nvolvulus Distri utio n : and Re io ns ycl p , x . b L g , C ae See Po m a yclosto m atid .

tiidm. Distribution M arine Pro ” C l dri tes acutus xii . vin ces 62 y in , , robultina Diwara 1 2 Cyli nd , 47 , 4

C t um olearium viii . Do co l ossa 10 2 ym a i , xx g , , 4 - D Periwi n le ee Pur ura. C m ba 88 o k . S y , g p - buli a 6 1 D o helk . See Nassa. Cym , g W

mbuli a roboseidi a vi . Dotabella Rhum hii V . xii . Cy p , xx p , , r Co wr 2 2 1 6 Dolium Cyp a a ( y), , , 3 , 97 , 94

rz a Al oensis . Dolium erdix ii . Cyp g , x p ,

a ca ensi s v. Dolium alea . Cypm p , g , x m a uttata 1 Donax 1 1 Cyp g , 44 , 9

C m a m oneta 1 2 D onax dentieulatus viii . yp , 4 , x

m a testudinaria vi . Dori s Cyfi , xx , 74 rian 6 Dosi ni a exoleta xi x Cyp , 3 , .

C ri na I slandica viii . D ata 122 yp . x , ren ide 8 Data coronata 12 Cy , 49 , 5 , 3 INDEX 1 49

i ssensia Zebra M ussel 0 E o astric Shell 1 Dre ( ), 3 x g , 7 — 8 2 1 1 0 E es 8 1 1 1 i . 5 . 9 . 34 . 4 y , , 3 33 , xx x

rei ssensi a ol mor ha xv X . D p y p , VIII , na a 1 xxxil . Faeeli na coro t , x 1.

D ru a arachnoides v . Fasci olari a tuli a xi . p , p , Dwarfin 1 1 Favorinus branchi alis Em br o g , 3 , y ,

D es e tracted ro m M o l lusca i . y x f , xx x Feedin tra ks 6 143 g c , 7 i c F us, 134

Ecc liom halus B uckl andi v . Ficus ventricosus i i . y p , , xxx ' Fil i nc i Echinos ra, 93 bra h a, 34 s M llusca 8 Fi rola 6 gg o o , 9 , 9 ’ - Fissurella 0 El e han t s Tusk Shells . See 1 p , 95 , 3

Dentaliidae . Fi ssurella Sta esi n ro wth i . , g g , xx x l i 1 1 1 6 Fi ssurella Li steri i x E ys a, , 2 , . l li El si a vi ri i s xii . Fissure dae y d , , 24, 5 3 , 94

- Emar inul a Flat co i led Water Snail . See g , 94

Em ar i nula ssure Pl anorbi s. g fi , VII . Em bletonia ulchra xii Fo o d fo r Ani m l s M o ll usca as p , . a , , Em br o n ic hell 1 6 y S , 9 , 94 7 E ndodonta 1 Fo o d for M an M o llusca as 8 , 9 , , I 3 E n do astric hell 1 Fo o d o f Mo ll usca g S , 7 , 67

En i na turbinella xi . Fo o t 2 16 0 1 1 g , , , , 3 , 35 , 4 Ensis R az o r Fi sh 1 1 8 Fordi lla ( ), 49 , 55 , , , 45 1 1 I I Fresh -water Marine M o ll uscs 9 . 3S, 35 ,

Ensi s sili ua xix . . in q , , xxx . 5 3 ' - Enteroxenos 82 Fresh water im et . See Anc lus. , L p y Entocolax 82 Fresh - a er M ll uscs — 8 , w t o , 5 7 5 - E ntoconeha 81 82 Fresh water M ussels . See , , h i En t n i 2 . o co c dae , 13 U n o nidae

- Ent si hon 8 Fr sh w er Pe rl M ussel . See o p , 2 e at a Entoval va 81 10 M ar ari tana , , 9 g . E oli s Fu nnel o f Ce hal o o ds 6 , 74 p p , 5 E o teri a Fus p , 45 us , 97

E hi odonta 2 80 10 Fusus eolus v . p pp , 7, , 9 , E i derm i s p , 3 ' E i hra m Gadzni a 10 p p g . 73 , 5 3 , 3 E i stethe 82 Guai ni Peruvi ana vi a . p , , xx E iton iiclae 6 Galeom m a Turtoni vi ii p , 4 , x . E itonium 1 26 Galeom m idae 2 p , , 7

E itonium reti osa v . G an li a 6 8 p p , g , , E i iu Gastro ch aena 2 ton m Turtoni s ra ula iii . p d , , 3 , 33

E ui valve 1 Gastrochana m um i a xi x . q , 3 . E ulam elli ranchia G astro o da 1 6 1 b , 34 p , , 5 u G eo lo i al Hi sto r E lim a, 81 g c y , 44 Euli m a oli ta vi Geom alacus Kerr Slu 1 20 p , xx . ( y g), Geo elani a 0 Eur bia Gaudichaueli vi . m 6 y , xx , Euth neura 2 8 Geoteuthi s 1 1 1 y , 23 , 4 , 7 , 49 , E i Gi n t Cl Tridac a volut on , 100 a am . See n . 1 5 0 THE LIFE OF THE MOLLUSCA

ib uta ci n u ii Helix nem orali s m andible In . G b erea rad l a, i . , Gi b Helix Pi sana 1 1 bus , 98 , 3 H li i m n Snail Gi bbus L onetanus ii . e x am el a R o a y , xxx p ( ), 73, — Gills 2 8 2 1 2 8 1 1 i v . , 7 , , 9 , 3 , '

Gi r le f Chi t s 1 Helix om atia : radul a iii . d o o n , 5 p , Gi z z ard 6 12 Helix tri sti s 60 , 9 , 4 , Gl aucom a 8 Heli x Veatehii y , 5 , 75 Glaucu A tlan i x i i Hel m i ntho chito n 6 s t eus, . , 4 Glochidium 82 Herm a hro iti sm 8 , p d , 7 Her ua i i Gl eim eri s lati tans xvi m b da 12 1 x i . y , . fi , ,

Gl eim eri s eel ini orm is xvu . Herm au dendri ti ea 12 1 y p f , , Gl tos m a 1 Hetero m arian yp o , 2 y , 34 Gonatus 1 2 Hetero o a 6 10 1 1 , 7 p d . 5 , 5 , 7

G re lu ee Limaz m axim us . Hetero stro h 1 y S g . S p y , 9 G r w Hin e l ine 2 o th , 5 g , 3 G r haa arcual a 8 Hi n e late 2 yp , 9 , xxx . g p , 3 Guar o f Belem n ite 0 Hi n e teeth o f i valves 1 d , 4 g b , 3 Hi nnites si nuosas vii , x . H abi ts of M o ll usca 6 Hi on cidae 10 , 7 p p y , 3 H alio tidae 2 Hi on x 68 , 4, 5 3 pp y , H alioti s rm er 1 1 2 0 2 Hi o us 1 06 ( O ), , , 4 , 5 3 , pp p , Hi o us m aeulatus x ix pp p , . Haliotis l ubereulata Hi uritidae , VII . p p , 49 Ha ite Holo ce a m s, 38 p , 45 H i i i Ho lo st m ato us shell 2 am tes attenuatus . o s 0 , xx , H ar a 6 1 1 6 1 2 1 H o m in in stinct 1 p , 3 , , 5 , 35 g , 37 H ar a ventri cosa xi H alaa 6 1 i , . y , He rin H alim ax 106 a g, 9 y , H eart 12 H bernacul um . 6 . 7 y , 73 Hecto co t li z atio n 88 H bern atio n 2 y , y , 7 H eleion H dro cenidae 60 , 5 7 y ,

H eli earion 1 6 H erstrO h 18 iv . , 3 yp p y, , Heliear on ti rinas 1 2 H ostracum i g , 4 yp , 4 e l ea a H selostoma 8 H liee la eonspur t , 78 yp , 9 H elicella itala , 77 Helicella vi r ata 1 1 Ianthina Pur le Sea Snail 6 g , 4 ( p ), 5 .

Heli ei ona la icida iii . 6 80 8 1 16 126 12 1 2 g p , x 9 , , 9, , , 9 , 3 , Heli ci ni ae 60 1 d , 43

H elicoceras rotundum ii Ianthi na ra ilis x . , xx . f g , , xxx. li aeeus viii H eli eost l a 120 Im erator o v . y , p , Helix 12 8 Incubator M o llusca 1 , , 4 y , 9 Helix as ersa Co m m o n G ar en Ine uil ateral 1 p ( d q , 3 Sna l 1 2 0 126 1 In e uivalv 1 i ). , 75 . 9 . . 37 , q e, 3 x Ink -sac 6 xxx , 3

Helix desertorum 6 1 12 0 iii . Inoceram us 1 1 , , 75 , , x , 4 Helix hortensis ee in tracks I hi enia , f d g , p g , 5 7 vii I soea/rdi a 10 xx . , 7 '

Heli x lactea 1 Isocardi a hum ana viii . . , 7 , x , xxx Helix nem rali s 1 I m ri an o , 77, 39 so ya , 34

1 52 THE LIFE OF THE M OLLUSCA

M all M ucus use in crawli n and eus vulgari s. xvu . d g M an di les clim bin b , 9 g , ‘ M an i li i i M urchi som a g a taniata, x . , 45 M urex 68 1 M an tle, 2 , , 69 , 43

M M urex haustellunt xi . an tle cavit 36 , - mtl e o eni n in i valves 2 M urex alm a rosa v. p g b . 7, p ,

sv M urex ramosus ii . . , xxx

M r M urex tenuis ina v. a gari ta, 63 p ,

M ar ari ana mar ari ti era Fresh M ussel Com m on M arine. See g t g j ( ,

water Pearl M ussel 1 0 M tilus. ), 4 y

M ar inella 6 12 M ussel s Freshwater. See Uni g , 3 , , M arine rm s o n 5and o ni dm o , f , 5 9 - M eli M arisa cowi u arietis, v. ut dae, 5 8 M artesia acuminata 6 1 , xx. M M. 35 . 5 7. 3 . 33

M edicine Snails use in 1 0 M a truncate xv xxx. , d , 4 y , ., M e alo on ti ae 6 M idz 108 g d d , 4 y ,

M e as i ra clatter iii . M oehama anomaidss . g f , x y , xx M elam m 1 M O sida 2 1 2 j s, 16 y p , 4 , 3 M el an 8 2 88 1 M tilidae 6 1 1 2 ia, 4 , 5 , , 9 y . 9 . 4 . 09 . 3 M el iidae M tilus Com m on M ussel 26 an , 5 8 y ( ), , M ela o si s 1 0 1 12 n p , 5 2 34s 5 3 : 541 57» 6 , 74s 1 7 1 1 M elea ri na Pearl O ter 1 1 g ( ys ), 5 , 3 M tilus Cali om ieus 140 y , M elea na b bat xvi M tilus edu i s 6 1 gri ar a, . y . ‘

M elea ri na mar ari ti er xvu M tilus samara dinus vii i . g g f , . y g , x e eena a M ortoni x vi M eom eni a Ban ulensi s Em r o M r ri , . y y , b y ,

i ne xix . i . M eretri x d o , xx x e ium 1 1 M tap od , 7 Nacreo us la er Metastraeon. 106 y , 4 2 N assa Do -Whelk 2 68 M i mi cry, 1 3 ( g ), 4 , 54, ,

alis xi . 8 10 Mitra episcop , 7. 4 '

M itrul ari a Dill u mi . N assa am i lawa xi . g , x , M odi olaria 6 N essa callosa 1 2 , 3 , 4 N assa neritea M odiolari a mem orata, 80 , xx. N assodonta, 58 i N atal iua o xx x. , 7 ri sm s N afie 1 2 M odioloides p , 45 a g 3 j 11 M odi olus Volsella . M o isture nee o f 0 , d , 7 definiti on 1 M oll usca, ,

C r 1 2 N ati ca mami ll a vi . M o ney ow y 4 , , ' N atiea m onth era ra ula ii i M on o m yaria, 34 f d , .

ata xix N atiea Reeluxiaua vi . M onopleura imbric , . , Naticidae 2 M ontaeuta, 80 , 13

on acuta substri ate viii . Nau til oidea 1 6 1 10 M t , x , 39, 4 , 4 , M on e Shells use fo r 1 2 Nautil us 10 6 6 0 y, d , 4 , 5 , . 35 , 3 , 4, 7 , M orum eaneellata v 88 1 10 1 1 1 11 12 1 2 1 1 , . , , , 9 , 7 , 3 , 4 , xxl M o ther o f Pearl, 4 .

M outh o f Shell , 19 INDEX I SS

N au i lu i u r r ee Hali oti s t s rad at s xi i . O m e . S . , x N eomeni a eari na rn m en t uses f r 1 0 ta, ix . O a , o . 4 N eom eni an s Orn am en tati o n 2 1 , 69 , 5 , Neom n ii na 1 8 rthoceras e , 5 , 7 O , 37

N e tunea 6 Orthoceras Ludense x i i . p , 3 , x N e tun a an i ue rtho re 1 p e t q , 5 5 O gy , 3 N erita 2 1 Oseani us 1 2 2 , , 57 , 63 , xii N erita ustulata, ix . Oseanius m em branaceous , . Neriti ae 10 Os hradium d , 3 p , 9 ri n r N e ti a Theodoxis Ost acum , 4 N eritodr as Ostrea O ster 2 6 y , 59 ( y ), , 34 , 35 , Nerve c n s 8 8 8 1 12 11 1 e tre , 6 3 , 9 , 9 , , 9 , 33 Nervo us s tem 1 iii Ostrea cornuco ia 8 ys , 7 , 13 , . p , 9

Nidam ent al ri bo n 8 Ostrea eduli s E m br o i . b , 9 , y , xx x

No rth ern ran e o f M o llusca Ostrea Rieordeana viii . g , , x

60 Ostreidae , 109 N otare us 1 1 Oto c sts h , 7 y , 9 N le f ell O vi aro us M oll usca 88 uc us o sh , 19 p . N ueula Nut hell 2 10 Ovo -vi vi aro us M o ll usca 8 ( S ), 3 , 34 , 6, p , 9

1 18 Ovul a, 1 2 1 N ueula ldi v wenella Cobbo ee, x u . O , 45

N uculidae 10 Ox urus Keraudreni vi . , 9 ygy , xx

Nudibran chia Sea Sl u s 2 O ster . See Ostrea. ( g ), 5 , 69, y 8 0 1 ster ul re 1 0, 1 5 , 30 Oy c tu , 39 Nu h l N ueula O sters o n rees t S e l s . See . y t , 54

Ocean - swim m in M o ll usca 6 Pace of a Sn ail 1 1 g , 5 , 5 ' Octo d P in ter s M ussel See Uni o p o a, 4 2 a .

Octo us 1 2 1 icl oram . p , 43 , 75 , 3 , 37 p dost i 1 n h 10 O om a, 9 Pal aeo co c a, 34 . 46 , 9 Oi o sida 2 1 2 P alaocto us g p , 4 , 3 p , 43 leaeina o P alwoeto us N ewboldi 1 1 1 O , 7 p , 49 , Ol acto r sen se Palli al lin e f y , 9 , 33 Oli va 6 1 1 Pallial si nus , 3 , 9 , 33 Oli va r h ri a xi P aludestrina therm ali s 1 po p y , . , 7

Oli uella as idea xi . Paludestri nidae 8 j p , , 5

Omniastre hes iv . Pandora ina ui valvis . p , xx q , xx

Oncidiidae 6 P ano ea Am ericana xi x. , 9 p , A onauta 1 P il u . e r Oncidium 106 a er N aut s S e . , 5 3 , , 33 p g On ehoteut i s Ba ksii xxv Parasi tes o f M o ll usca 8 y h n , . , 7 , 79 P r i ic M o ll usca 81 82 Opeas , 88 a as t , ,

O en in shells fo r re 6 P arm aeell a cal cul ata iii . p g p y, 9 y , x

O ercul um 2 2 6 Partala aba iii . p , , 9 f , x O ercul um t es o f viii Patella i m et 10 p , yp , . (L p ), , I I , 5 3 , 94 , O i stho branchia 2 1 26 10 1 2 1 2 I p , 5 , 3 . 9. 3 , 37

O istho re 1 Patell a vul ata ix . p gy , 3 g , 5 3 , Pat ll uul ata radula iii O i sthostom a 8 e a . p , 9 g , ' P li 10 O isthostoma randzs inosa ii . atel dae p g p , xxx , , 5 3

O u is Patina Pellucida i x . pisthote tli , 43 , 1 5 4 THE LIFE OF THE MOLLUSCA

rl cl a ri na i sidiu 2 Pea Oyster. See M e g . P m, 59 . 9

Pearls 1 0 1 1 Pisi dium am nicum xv. , 5 , 4 , 4 , i f Placuna l acenta 1 1 Pearls, o r gi n o , 79 p , 4 Pecten Scallo hell 1 12 Planktom a 11 ( p S ), 34, , y , 9 Pl an o r idae 8 b , 5

P ten. i mus Plan orbis Fl at co ile Water ec max , 5 5 ( d Pecten o ercularis Snail 10 18 8 0 p , 55 ). , , 4 , 73 , 9

Pecten vari us xv . Planorbi s corneas iii . . , x P lat ra P ectenacea, 133 yce s, 44 i i i l li Pect nate gill , i . P eural gan a, 8 Pectini ran chia 2 P leurobran ida 1 2 b , 4 , 3

Pectinidae, 46 P leurobranchus, 13 1 P cuncu l ci meris P l u e t lus G y e roceridz , 58 Pe al an lia 8 P leurodonta crassi labri s 1 d g g , , 35 P lcurodonta imperator. 135 P cdi cs 1 1 P leur p . 6 o podia, 116 Pedant s ond l xv u p y oides, . Pleurotoma, 20 Pela i a al ba vi P leuratoma B ab lonia vu xi 1 g , xx . y , . . . Pel ec o da 2 6 1 1 0 12 8 12 yp . , 5 , 3 20, 12 5 , , 9 P en-and-Ink Fishes 2 Pleurotom ari a Adansoniana 1 , 4 , 44 Peri o stracum Pleurotomari a An lica vii , 3 g , . Peri her 1 P licatula p y, 9 , 64 Peristom e 1 Pneumoderma violaceum vi . 9 , xx .

Periwinkle . See Littori na. P oli ta o 12 , 7 , 6 P crna 6 Poli ta cellar a C ll nail 68 , 3 i ( e ar S ). ,

Petri cola haladi ormis 1 xxxu. i i . p f , 34 . x i Petricoli ae P ol ra hirsute viii d , 49 ygy , .

Phasi anella Aus ralis ix. P ol ra th roides 8 t , ygy y , 7

Philine 1 1 1 P ol ratia ol rata iii. , ygy ygy , x

Philine a rt xi i . l l pe a, P o yp aw p 3 . P hilo a 82 2 O us 1 10 bry , , 9 ( ctop ), 36, Philo br id 10 y a , 9 P hil om 1 ycus, 06 Pholadella 6 P ol ms tuberculatus : m an i les , 4 fl d b , Phaladidca, 98 P hol a candida l ul m n to adomy , xx. P o yims v garis (Co m o Oc Pholas Pi ock 1 1 1 uS ( dd ), 54, 9, 33 p ).43 Pholas icola P ri v , 57 omati as , 77 Ph ra m ooone 0 P om ati as el ans 8 viii g . 4 eg , 7 , . P h lli y rrhoé. 56. 105 Po m atiidaa, 60, 1 16 Ph sa Bu le Snail 6 Po n M ussel ke t m an a s y ( bb ), 5 3 , 5 , d , p y d y 10 f w ‘ 5 o ut o atel . 75 Ph sa onti nalis iii Po nd Snail s 8 y f . x . , 5

Ph sida 8 P arom a h alina . y , 5 y y , xx

P h ti a m osoti s iii . P r ii y y , x o o m y dae, 35 Pi ddo k c See P halas. . Po sterio r Canal , 20 Pi nna 1 1 1 1 2 P ot mid s , 4 , 33 , 4 . 4 a e , 5 7

Pi nna nobilis viii . Pri scochi on , x t , 46 , 102 Pi nni e 6 Pro isso co nch 0 d , 4 d , 3 , 94

1 56 THE LIFE OF THE M OLLUSCA

Se ia C uttlefish 2 8 1 1 0 S he rium corneum xvu i . p ( ), 4 , 9 , , p , iv S iral cleava e o f E xx . p g gg, 93

Se i a o i ci nali s xxv . S i ralis buli moides vi p fi , p , xx .

S e i a g ici nalis E m br o i . S irula 2 iv . p fi , y , xx x p , 39 , 4 , xx

S e i ol a atla tica r ul iii . S i rul a P eronii x x v p n : ad a, p , . Se i a 6 S irulirostra i v p , 3 p , xx . S iruli rostra Bellardi i xx v Se ta tri toni s v i . . . p , , x p , Se tari a 8 0 10 S o n d lidae 8 p , 5 , 9 , 3 p y , 4 e tibr nchi S ond lus 6 8 1 S p a a, 35 p y , 3 , 9 , 33 i er 1 S ond lus rince s i S e t v i . p f , 34 p y p p , x Se ti er bilocul aris i i S ond lus vari as 8 p f , xxx . p y , 9 , xxx . Se tum 2 1 S on i obranchia aus i 1 vi tral s 6 . p , p g , , xx Se tum o f Ce h alo o d Shell Steno lo ss 2 p p p , 38 g a. 4 Se ual di m o r hism 8 Steno ridaa 0 x p , 7 gy , 9 Shell 1 S teno us 1 , 3 , 7 p , 35 Shell li m e fo r obtai ne ro m Stenotheca , , d f , 44 " o o 6 Stenotrem a hi rsuta i i i f d, , x . Shell rem o val o f ortio n 2 1 Stili er 81 , p , 5 , f , Shell a erture m o des o f clo si n Stili er astericola vi p , g, f , xx . 2 1—2 Stili eri na 81 3 f , Shell M o ne 1 2 Stomati a h m tis ix y , 4 p y o , . Shell si hun cle Stra arollina p , 39 p , 45 Shell to o ra h 1 Stre taxi s con tusus x111 p g p y , 9 p , . Shell tubes o f bi val ves 2 Stre to neura 2 8 y , 3 p , 3 , 7 - Shi wo rm . See Teredo Strom bus 2 2 80 10 1 1 1 2 p . , , , 97 , 4 , 7, 4 Si aretus 1 16 Strom bus auri s-Diana' viii g , , . Si aretus hali otideus x Strombus i as 1 1 g , . g g , 4 Sini stral Shell s 1 8 Strombus Mauri tianus 1 , , 34 Sinusi era Stram bus u ili s g , 94 p g , x . H u l i v Stro hi tes Si nusi era x e i . g y , xx p , 47 Si ho n o f Ce halo o s 6 S tro hochei lus 0 1 0 p p p d , 3 p , 9 , 5 Si hon s o f bi valves 2 Stro hocheilus oblon as xi i i p , 7 p g , . i h ri Stro hocheil at S ona a 1 0 us ov us . p . 5 3 , 3 p , xxx Si honari a Kurrackensi s vi S truthiolaria viii p , xx . , . Si ho n ariidm 6 St li er 1 1 8 p , 9 y f , Si ho no sto m ato us Shell s 2 0 St li er br chius 6 p , y f y , 5 Sm ara di nella vi ri is xii St l o m m ato ho ra 2 60 g d , . y p 5 ,

Sm ell Subemar i nul a ru osa i x. , 9 g g , n il l v i 1 ub M l S a cu ti at o n , 39 S yti acea, 5 8 Sn ai l easts 1 Subuli tes f , 39 , 45 S olecurtus 1 S uccinea , 35 5 9 , 79 " Solen 1 1 8 Succi nea atris i i i , p , x . So lenidae 1 08 Sum s aid for Shells 1 , p , 44 So len o co n ch a 2 Suture 1 , 5 , 9 So leno astra 1 Suture line g , 5 , 39 Solenom a 1 1 Swan M y , 9 ussel . See Anodonta Solenom a to ata xvn y g , . S eki a 1 S cot us 6 1 p , 9 y yp , 9 , 34 S hxri um 8 2 1 18 S cot us rum x i i p , 5 3 . 5 , 9 , y yp py , x x . INDEX 1 57

Taenio lossa 2 12 Tri onia costata viii g , 4, 5 g , x . Tri onia ecti nata g p , xxx . Ta es Tri o niidae 6 p 5 4 g , 4 Ta o ont 2 Tri onochl am s 106 x d , 3 g y , Tecti ranchi a 2 10 Trivi a E uro wa ii b , 5 , 5 p , . Teleo ont 2 Tro chidae 6 10 d . 3 , 5 , 4 , 5 4 , 3 Tel li na 108 Trochonem a , , 45 - Tellina lin ua elis viii . Trochatom a conul oides vii . g f , x , Tem erature ran es en ured Trochus 1 1 p , g d , , 1 Tro hon 7 1 7 2 p , 63 Tena odes 8 Tro hon Geversi anus xi g , 9 p , . n odes austral is v Truncatella 60 Te ag , , , 5 7 , atmn Turbi nella 10 1 Tercbellum snbul . 1 , x , 4, 4 Turbi n a Terebra 6 10 2 1 2 el l rum xi . , 24 , 3 . , 3 py , T bra aculata xii n ida ere m , . s 5 1 103 n ta xx Turbo uctua vm Teredi i a ersona , . fl tus , . - o i wo rm 2 Turbo m arm oratus i x. d (5 v ). 3 . 33 . 35 . , Turbo neri toi des, 5 3 T rve ica Turbo sarm a ii eredo N o ti cus v i . g , xx. , T Mo lluscs 60 Turbonilla 1 errestrial , , 9 Tes acella 60 0 Turbonilla di s cha i v t , , 7 p y , . Turri ul Testacell a hali otidea iii . c a vul ecula xi . , x p , T a l ul m xi v Turri lites costains ii est cel e scut u . , , xx .

Teth s le orina x ii Turritell a i m bricata . y p , . , x Tetrabr n hia 1 T ho biidse 8 a c , 4 yp , 5

Thecalia concani erata, 92 Theodoxis 1 2 6 U m bilicus 1 , 2 , 5 , 5 3 , 5 , , 9 0 10 U m bo 0 9 , 3 , 3 T b a i Um bonium uest a heodoxi s ze r , x. i rimn, ix. Thorn er See S o nd " Um bracul um 1 2 y Oyst . p y , ‘ lidae Um o 8 6 2 1 . . 5 . 4 . 5 3 . 5 . 9 . 1 4 Thraci a ubescens Uni o batavus 88 p , xx . ,

Th ea 81 Uni o li ttoralis viii . y , , x ’ Th ro horella 2 6 vi i i . Uni o ictorum Painters M ussel y p , 3 , 4 , p ( ),

Ti edem annia Nea oli tana vi 8 x v . p , xx 9 , Ti i a 10 Uni o tumidus 88 tiscan , 5 , To hell s 1 1 U ni on idae Fresh w r M s p S , 5 , , 5 4 ( ate u sels), 8 80 82 5 . 5 . . . 9 7 Tom a n v luta x ii U roco tidae 8 ti a o , . p , 9

Torsi on of astro o o 16 Uroco ti s c lindras iii . g p d b dy, , p y , x

1v.

Toxocaras annulare i i . Va inella de ressa vi . , xx g p , xx To o lo ssa 2 1 2 Val vata 8 1 2 x g . 4 , 5 , 4 , 9

T l sa Val uata cri stata at . rachyg os , 43 ,

Tricli oc clus Dum ril i vi . Val uata i sci nali s . y , xx , p , x Trichotro is 6 V al vatidae 8 p , 3 , 5

Tri dacna 6 80 Vani coro cancellata . , 4 , 74, , , x V ari an d Varic s 2 0 I x e , - Tri oni a 1 Vasurn corni er um xi . g , g , 158 THE LIFE OF THE M OLLUSCA

V lates 6 Voluta 6 e , 9 , 3

Vel etas conoideus i i . Voluta ra ula iii . , xxx d , a e Voluta undul ata ii Veliger st g , 6 , 93 , . Vul sella 6 Velum , 93 , 3, 80

Vel utina, 63 Veneri ae Venus Shells am um 1 2 d ( ), 35 , W p , 4 10 Water m ains invad ed by M ol V Zmercenari a l usca enu , , 59

Venus a hia xix. Water n ils 68 p p , S a h ll s V n idae te - h Ven us S e . ee e er . a r t S ell S W po . See Brechi tes. Verm etus 2 1 8 1 18 h el ci u , , 9 , W k . See Buc n m .

Verm etus lumbri cali s i ndow Shel l . See Pl acuna , x . W . dii W - Verti cordi a car o mis . o m eatin Slu s . See T t f r , xx g g es a Verti o an usti ar i ii ccfla g g , x . . Veroni cell a 1 06 , Visceral an lia 8 Xeno hora 12 g g , p , 2 Vi sceral h um 1 X eno hora conch lio kora viii p , 7 p y p , xx . Visceral lo 8 eno hori ae 6 w, X p d , 4 Vi tri na an eli ca 60 Xesta Own i 12 g , ingi , 4 Vi tri na el lucida ii i X lo ha a dorsali s p , x . y p g , xx . Vivari a for O sters 1 X lo a l r bi innata . y , 39 y y , p , xx Vi vi ara 6 8 p , 5, 7 , Vi ara contecta v i i vip , i .

Vi vi ara vi vi ara ii . 11 Yoldi a 6 p p , , . , 3

Vi vi arid 8 Yoldi a ali s xvn . p ae, 5 my , i vi r u M l s 8 V p a o s ol u ca, 8

Volsella 1 2 2 Ze ra M ussel . See Dreissensia. , 5 5 , 5 7, b