An Outline of the Principles of the Natural Selective Absorption of Radiant Energy

¾ol.1925 XLII] ] CARTWRIGHTANDI-IARROLD, Radiant Energy. 233

AN OUTLINE OF THE PRINCIPLES OF THE NATURAL SELECTIVE ABSORPTION OF RADIANT ENERGY. t

AN HYPOTHESISGIVING A NEW INTERPRETATIONTO THE MEANING OF COLOR WITH SPECIAL APPLICATION TO APTOSOCHROMATISM.2

BY B. W. CARTWRIGHT AND C. G. HARROLD.

I. OUTLINE O• Tt•E PRINCIPLES.

The only known sourceof energyin the planetary systemto whichwe belongis the Sun. All manifestationsof kineticenergy can in final analysisbe referredto that sottree. It is the relation betweenthis first greatfundamental, energy, and the secondgreat fundamental,matter, that engagesthe attentionof thinkingpeople all the world over. To find and conserve for the use of mankind new methodsof utilizing the energyso lavishlyshowered upon the earth by the Sun,is the aim of many devotedscientists and howim- portant this objectis to civilizationcan be imaginedwhen we try to think what would happenif we suddenlywere deprived of coal. This is the age of coal,generally speaking, although a few favored placeson the earth'ssurface augment their e.nergy resources by oil and water power. Theseresources have their origin in solar radiationsstored up ages ago in the easeof coal and oil and con- tinuouslyin the easeof electricity derivedfrom the flow of water to the sea. a Let us first deal with energy. We find that it manifestsitself in the form of electro-magneticwaves of almostincredible minute- ness but neverthelessmeasurable with great exactitude in ten- thousandthsof a centimeter. The total range of wave-lengths detectableby our instrumentsis as follows: I ' '•1 ! SchumannWaves .00001to .00002cm. nwsme'•Ultra Violet .00002to .00004cm.

• Revised from papers given before The Natural History Society of Manitoba, Dec. 27, 1922, Mar. 24, 1924. ' A, privative, ptosis, to fall off, chroma, color. • Loc. cit., 'Matter and Energy,' Frederick Soddy. 234 CARTWRIGHTANDHARROLD, Radiant Eneryg. [AA•l

(Violet .00004cm. Visible •Green .00005cm. IRed .00006 to .000075 cm. Infra Red .000075 to about .0001 cm. Rest Strahlen from quartz .00085 to .0020 cm. " .... sylvite .0060 cm. The longestwaves are sixhundred times the lengthof the short- est. Thecorresponding •ange of wave lengths of sound would be a little more than eight octaves,of whichthe visiblepart of the spectrumis lessthan one. • It is importantto bearin mindthat thewaves capable of producing in our brains the senclarion ofvision are a very smallportion of the total energyreeelved from the Sun. When we speak of light in the pagesto follow, we refer to this limited part of the spectrum,but when we speak of "Radiant Energy" we refer to the wholeof the solarspectrum both visible and invisible. Matter is nowgenerally accepted as beingelectrical in structure? the nucleusor protoncarrying the positivecharge and the electrons carryingthe negativecharge. In the periodictable of elements, theatomic numbers 1 to 92 representthe numberof electronsthat are attachedto the proton of eachelement. The principalfact that concerns us here is that each element has a characteristic absorptionof radiant energy,i.e., eachelement takes in spedfie wave lengthsof energyand no others. Let us be quite dear on this point, different thicknessesof different media may show variableabsorption of radiantenergy but the absorptionwithin an atomicsystem, i.e., its proton and attendantelectrons, is definitely characteristic. We are now in a positionto dealwith the phenomenonof color. Whenradiant energy falls on an object,part of it is reflected,part is absorbedand part is transmitted. That part whichis reflected and which lies in the region betweenwave lengths.000075 and .00004,gives to us the sensationof color. With birdswe havebeen taught that coloris an adaptive meansof harmonizingwith the environment,the object beingto attain concealmentfrom enemies (orvictims) and thus serving the principle of natural selection which is survival of the fittest for the preservationof the spedes. The

Phillips, ' Radiation,' pp. 80. Rutherford, Nature, p. 183, NO. 2753, Vol..110o ¾ol.1925 XLII] ] CARTWRIGHTANDI-•ARROLD, Radiant Energy. 235 adaptivecoloration theory of Darwin, however,is basedsolely on the vlsual appearanceof'those waves of energythat are reflected from the bird andwhich lie withinthe rangeof wavelengths capable of excitingthe sensationof sight. Experimentshows, however, that very oftenif not always,there is reflectionof wavesin the invisible parts of the spectrumthat canhave no bearingon the questionof concealingcoloration. To our minds this is a conditionthat throwsgrave doubt on the adaptivecoloration theory as a complete explanationof the meaningof color. There is, however,a more seriousobjection still, namelythat the reflectedwaves are in fact rejectedwaves of energyand that the bird is taking out of the radiant energycertain sections which it is absorbing. In view of the constantrelation betweenenergy and its absorptionby matter, the convictionthat we are dealingwith somethingmuch more fimdamentalthan visual appearancesis unavoidable. On this view, coloris merely incidentalto "That intimate assoclateshlp betweenliving energeticsand inanimateforces of whichbiology is only beginningto form a conception."1 The first important conclusiontherefore is that the adaptive colorationprinciple is only part of the bird'sfitness for its environment. Our next considerationis to enquireas to the use made of the radiant energyabsorbed. What part doesit play in the economy of the bird? Beforewe can deal with this questionit will be ne- cessaryto go into someof the known effectsbrought about by the absorptionof radiant energyby matter generally. It is only the radiant energythat is absorbedthat is active in producing chemicalchange. This is known as Draper's Law. When such changestake placeunder the influenceof radiant energy,they are knownas photo-chemicaleffects. The formationof chlorophyllis a photo-chemicaleffect and the functionof chlorophyllin the pro- cessof photo-syntheticcarbon assimilation is alsoa photo-chemical effect. "The converse,that all light which is absorbedgives rise to chemicalaction is non-proven,the absorptionspectrum of a chemical systemis intimately connectedwith its photo-chemicalbe- havior." •

Ganable, 'The Animal World,' p. 142. Sheppard, 'Photo-Chemistry,' p. 140. 236 CA•Tw•,• A•VDYD, Rr:OLD, Radiant Energy. [AprilAuk

"It appearsthat the absorptionof light, the conductionof electricity and the chemicalreactivity of a substancemust all be referred to a commonorigin." • This law of Draper'sis equallytrue in the caseof organicphoto- chemicaleffects such as the developmentof the tan pigmentin what we call sunburn. We must also mention the so-calledcatalytic action of radiant energy where reactionsare brought about to form compounds which are reversiblein the dark. The reversionmay be partial or complete. Often in the processa compoundmay be kickedoff on the side as it were, that is indifferent to the action of radiant energy. This seemsto be a very important point, abundantly supportedby experimentalevidence. It would appearto be intimately connectedwith the phenomenonof growth. Our secondimportant conclusion is that the absorptionof radiant energyby the bird is accompaniedby chemicalreactions and that variation in the colorationof plumagedenotes variation in the absorptionspectrum of the bird. We will nowproceed to a considerationof progressivechanges of radiant energy. It is known that the atmosphereand the finely suspendedpar- ticlesin it absorbthe rays of the sunprogressively as the thickness of the air increases. Supposethat above us there is a belt of at- mospherefrom fifty to one hundredmiles thick. The first rays of the risingSun passing through at a glancingangle will traverse a maximumthickness of air and asthe longestwaves penetrate.the farthest and as these wavesin the visiblespectrum give us the colorsensation of red, it followsthat the dawn often appearsred. The effectis frequentlymasked by the diffuseskylight, i.e., the shorterwaves reflected by the higherreaches of the atmosphere whichcombine with the directrays of the sun to give the eye the integraleffect of white light. Even after we havewhite light, the continued rise of the sun sends through to the earth's surface shorter and shorter waves until the maximum is reached at mid- day. This processmay be describedas the additive effect. After mid-day and until the gloriesof sunsetdelight the eye, we have the reverseprocess which we may call the subtractive x Sheppard, 'Photo-Chemistry,' p. 162. Vol.1925 XLII] I CARTWRIGHTANDI-IARROLD, Radiant Energy. 237 effect. This is the daily routine,but we have alsoa seasonalad- ditive and subtractiveeffect from vernalequinox to summersol- sticeand from summer solstice to autumnalequinox respectively.

Showingthe variation in the spectralcharacter of sunlightdue to atmosphericabsorption.

"The effectof differentmasses of air uponthe relativeamounts of energyin eachwave lengthhas beendetermined by Abney;his data are reproducedabove." • Note, these data cover the visible regiononly, but the variation in the ultra violet and infra red can be inferred. It will be seen that the variation in the shorter wave lengthsis muchgreater than that in the longerones. This is very significantas it is the shorterwaves, particularly the ultra violet, that possessthe greatestpower to producephoto-chemical effects. We should mention also that measurements of the chemical in- tensitymade by Roscoeand T. E. Thorpe revealedthat diffuse skylightwas more active than directsunlight until the sunreached a zenith distanceof approximately48 ø whendirect sunlight took the lead. Our third and mostimportant conclusion may nowbe stated:- That the absorptionof radiantenergy is the governingprinciple of the metabolismof a bird's body. Sofar we haverelated our hypothesis to the bird as it was a Luckiesh, 'Color and Its Applications,' pp. 38 and 39. 238 CARTWRIGHTAND•.ARROLD. Radiant Energy. •pUrril throughobservation on birds that our hypothesishad its genesis and development,but if the conclusionswe have presentedare verifiedby other investigators,it will hardly be necessaryfor us to statethat we are dealingwith a new biologicalprincipal of tremelywide application.

II. APPLICATION' OF THE I-IYPOTHESIS TO THE EXPLANATION OF APTOSOCHROMATISM.

Thereare severalspecies of birdswhich change from their winter plumageto summerplumage by losingthe tips of the feathers. A notableexample of this processis the SnowBunting which

o• •o changesfrom a rustycolor on the backto blackand white, without the lossof a singlefeather. The rustytips are lost,revealing the blackand white parts of the feathersbeneath. The generally ceptedexplanation of this processis that the tips are gradually worn off by the bird'swinter activities. Dr. Frank M. Chapman in his 'Birds of Eastern N. A.' taking Dwight and Strongas his authorities,illustrates the gradual diminution of the tips from Octoberto March, by whichtime the wearingprocess has culmin- ated iu the almosttotal disappearanceof the tips. We have ex- amined a number of specimensof the Snow Bunting taken at Vol.1925 XLII] ] CARTWRIGHTANDI-IARROLD, Radiant Energy. 239 variousplaces in Canada from Octoberto May and we have found no evidencethat the processdescribed above sctually takes place. We foundthe tips of specimenstaken in March and April to be just as longas tips of specimenstaken in October. In March we foundthat a white line had developedbetween the dark colored part of the featherand the rusty coloredtip. Under the micro- scopethis white line was characterizedby (1) disappearanceof barbicels;(2) missingor witheredbarbules; (3) bleachingof pigment granules. The microscopicexamination of the tips was checked and the resultsconfirmed by Chas.W. Lowe, M.Sc., of the Uni- versityof Manitoba. We examineda specimentaken in April at Norway House,Lake Winnipeg,a tertlal featherof whichis lustratedherewith (p. 238). Partof the tip has broken off at thewhite line. We experi- mentedon the tips with a pairof forceps and found that before the developmentof the white line the tip couldbe bent backwithout dangerof breakage,but after the white line developedthe same experimentwould snap off the tips at the white line. Field ob- servationhas shown that the developmentof the white line and the lossof the tipsis accomplishedin from three to five weeksin the springand that there is no evidence ofwear prior to the development of the whitellne. The tip itselfhas the barbicels,barbules andpigment granules intact when it is discarded,the disintegration taking placeonly in the area of the narrowwhite line whichis at the junctionof the rustytip with the darkerpart of the feather. We had workedout the abovewhen Mr. C. L. Broleydrew our attentionto the remarksof Dr. Elliott Couesin his'Key to North AmericanBirds' where we foundthe wholeprocess accurately de- scribedand to whichDr. Coueshas given the unwieldytitle of aptosochromatism. Togetherwith the SnowBunting (Plectrophenaxnivaliz) we foundthat the followingbirds lost their tips or parts of their feathersin substantiallythe sameway, the developmentof the white line beingcharacteristic of the process:- Group I. Lark Bunting (Calamospizamelano½orys) Lapland Longspur(Calcarius lapponicus) McCown's Longspur( Rhynchopha•es mcco•nii) 240 CARTWRIGHTANDHARROLD, Radiant Energy. [Auk[April

Smith'sLongspur ( Calcarius pictus) Chestnut-collaredLongspur (Calcarius ornatus) Brewer'sBlackbird (Euphaguscyanocephalus) Rusty Blackbird (Euphaguscaro•inus) Marbled Godwit (Limosafedoa) European Brambling (Frin•illa montifringilla) Group IL Bobolink (Dolichonyxoryzivorus) HudsonJanGodwit (Limosa haer,astica) Knot (Tringa canutus) Dowitcher (Limnodrom•tsffriseus) Stilt Sandpiper (Micropalama himantopus) Acceptingthese resultsas disposingof the wear theory, it is evidentthat a structuralchange has taken placein the feathersat theparts indicated by, the white line Onthe basis of ourhypo- thesisset forth in part I this changeis a photo-chemicaleffect brought about by the increasein chemicalintensity of radiant •nergy in the spring,i.e., when the additiveeffect is progressing. This conclusionenabled us to make an interestingprediction, to wit:That birds showing the tip phenomenonwould not go south of the equatoron migration. When it is notedthat if they did, they would run into radiant energyof the necessaryintensity to bringabout the lossof theirtips, it will beseen that this prediction formsan acid test of the correctnessof our hypothesis. When we cameto list all the birdswe know that showedthe tip phenomenon,we found that someof them did go southof the equator,so we dividedthem into two groupsas above. GroupI listsbirds which do not go southof the equatorand GroupII lists thosethat do. A striking and savingfactor was now revealed. All the birdsin Group I moult oncea year in the fall and the newplumage carries the tips whichbreak off the followingspring. The birdsin GroupII moult twice a year, first in the fall into a winter plumageand againin the springprior to their migration north. Only the springpre-migration plumage carries the tips and thosedisintegrate during the northwardjourney. Here alsowe have a relationbetween plumage changes and mi- grationthat opensup a widefield for investigation. The evidenceall pointsto a physiologicalexplanation of the mysteryof migrationand this we confidentlyexpect will be oneof Vol.1925 XLII] I AHRENS,Bird Collection ofBerlin Museum. 241 the achievementsof the applicationof the principlesof the natural selectiveabsorption of RadiantEnergy., œ98Ainsley St., SturgeonCreek, and •78 St. Mary's Ave., Winnipeg,Man.

THE ORNITHOLOGICAL COLLECTION OF THE BERLIN MUSEUM. •

BY T. G. AHRENS.

Tn• ornithologicalcollection of the Berlin Museumof Natural Historyforms an integralpart of the collectionsof the University of Berlin. Whenthe University was founded in 1810the zoological collectionwas also started. The first curato• of the collection was Dr. Karl Illlger,an entomologistof Brunswick. The beginningof the ornithologicalcollection was very modestindeed, but soona considerableincrease could be noted. Peter SimonPallas (1741- 1811),donated his bird collectionsto the museum,some of which werefrom Transbaikalia, collected in 1772. Most of thespecimens aredescribedin his ' ZoographiaRosso-Asiatica.' A fewspecimens wereobtained during a journeywhich Pallas made to the Caucasus regionsin 1793, and somewere collectedby Dr. Merk in Kam- chatkaand Alaskain 1790. In the sameyear that the collection wasfounded it waslargely increased by CountJohann Centurius yon Hoffmannsegg,a well-informed zoologist who maintainedre- lations with a number of well-known travellers and savants. An- tonio Gomezcollected birds for him in 1802 in Bahia, Brazil and Franz Wilhelm Sicherin the state of Para. The latter returned to Europein 1810,and although Illlger devoted himself particularly to the birdsof South.Mnerica, his investigations were not pub- lishedowing to his death in 1813. Illiger's successoras director of the museumwas Dr. Heinrich Lichtenstein(1780-1857), then 33 yearsof age,a physicianby training who had been tutor in the familyof the governorof DutchSouth Africa for fiveyears and had returned to Europein • All the data in this paper were obtained from Dr. Erwin Streseman, Curator of the Bird Collectionin the Museumof Berlin, Read at the PittsburghMeeting of the A. O. U.