3U<\ Bulletin of the Museum of Comparative Zoology AT HARVARD COLLEGE. Vol. LII. No. 13. REPORTS OX THE SCIENTIFIC RESULTS OF THE EXPEDITION TO THE EASTERN TROPICAL PACIFIC, IN CHARGE OF ALEXANDER AGASSIZ, BY THE U. S. FISH COMMISSION STEAMER "ALBATROSS," FROM L. M. OCTOBER, 1904, TO MARCH, 1905, LIEUT. COMMANDER GARRETT, U. S. N., COMMANDING. XX. MUTATIONS IN CERATIUM. By Charles Atwood Kofoid. With Four Plates. U. S. Fish. [Published by Permission of George M. Bowebs, Commissioner.] CAMBRIDGE, MASS., U. S. A. : PRINTED FOR THE MUSEUM. September, 1909. Reports on the Scientific Results of the Expedition to the East- ern Tropical Pacific, in charge of Alexander Agassiz, by the U. S. Fish Commission Steamer "Albatross," from October, 1904, to March, 1905, Lieutenant Commander L. M. Garrett, U. S. N., Commanding, published or in preparation: — A. AGASSIZ. V. b General Report on the Ex- H. LUDWIG. The Holothuriane. pedition. H. LUDWIG. The Starfishes. A. AGASSIZ. I. 1 Three Letters to "Geo. M. H. LUDWIG. The Ophiurans. Bowers, U. S. Fish Com. G. W. MULLER. The Ostracods. A. AGASSIZ and H. L. CLARK. The Echini. JOHN MURRAY and G. V. LEE. XVII." H B. BIGELOW. XVI. 16 The Medusae. The Bottom H. B. BIGELOW. The Siphonophores. Specimens. MARY J. RATHBUN. X. 10 The Crustacea R. P. BIGELOW. The Stomatopods. O. CARLGREN. The Actinaria. Decapoda. HARRIET RICHARDSON. II. 2 The Isopods. 8. F. CLARKE. VIII. 8 The Hydroids. IV. 4 The Tuuicates. -W. R. COE. The Nemerteans. W. E. RITTER. J9 ROBERTSON. The Bryozoa. L. J. COLE. XIX. The Pycnogonida. ALICE The Plants. W. H. DALL. XIV. 14 The Mollusks. B. L. ROBINSON. The C. R. EASTMAN. VII. 7 The Sharks' Teeth. G. O. SARS. Copepods. 11 B. W. EVERMANN. The Fishes. F. E. SCHULZE. XI. The Xenophyophoras. W. G. FARLOW. The Algae. H. R. SIMROTH. The Pteropods and Hetero- 12 S. GARMAN. XII. The Reptiles. pods. H. J. HANSEN. The Cirripeds. E. C. STARKS. XIII. 13 Atelaxia. H. J. The HANSEN. Schizopods. TH. STUDER. The Alcyonaria. 8. HENSHAW. The Insects. JH. THIELE. XV. 15 Bathysciadium. W. E. HOYLE. The Cephalopods. T. W. VAUGHAN. VI.« The Corals. C. A. KOFOID. III. 3 IX. 9 XX. 20 The Protozoa. R. WOLTERECK. XVIII. 18 The Amphipods. P. KRUMBACH. The Sagittae. The Annelids. R. VON LENDENFELD. The Siliceous Sponges. W. McM. WOODWORTH. i 22 Bull. M. C. Z., Vol. XLVL, No. 4, April, 1905, pp. * 4 1 Bull. M. C. Z., Vol. XLVL, No. 6, July, 1905, pp., pi. 5 1 » Bull. M. C. Z., Vol. XLVL, No. 9, September, 1905, pp., pi. 22 3 * Bull. M. C. Z., Vol. XLVL, No. 13, January, 1900, pp., pis. B 90 96 Mem. M. C. Z., Vol. XXXIII., January, 1906, pp., pis. 14 10 s Bull. M. C. Z., Vol. L., No. 3, August, 1906, pp., pis. 26 4 « Bull. M. C. Z., Vol. L., No. 4, November, 1906, pp., pis. » 20 15 Mem. M. C. Z., Vol. XXXV., No. 1, February, 1907, pp., pis. » 48 18 Bull. M. C. Z.,-Vol. L., No. 6, February, 1907, pp., pis. 56 9 io Mem. M. C. Z., Vol. XXXV., No. 2, August, 1907, pp., pis. 22 1 » Bull. M. C. Z., Vol. LI., No. 6, November, 1907, pp., pi. 14 1 u Bull. M. C. Z., Vol. LIL, No. 1, June, 1908, pp., pi. 8 5 M Bull. M. C. Z., Vol. LIL, No. 2, July, 1908, pp., pis. 285 22 M Bull. M. C. Z., Vol. XLIIL, No. 6, October, 1908, pp., pis. 11 2 " Bull. M. C. Z., Vol. LIL, No. 5, October, 1908, pp., pis. 243 48 is Mem. M. C. Z., Vol. XXXVII., February, 1909, pp., pis. 172 5 3 m Mem. M. C. Z., Vol. XXXVIIL, No. 1, June, 1909, pp., pis., maps. i 8 26 8 Bull. M. C. Z., Vol. LIL, No. 9, June, 1909, pp., pis. is 10 3 Bull. M. C. Z., Vol. LIL, No. 11, August, 1909, pp., pis. 48 4 2* Bull. M. C. Z., Vol. LIL, No. 13, September, 1909, pp., pis. JUSJ Bulletin of the Museum of Comparative Zoology AT HARVARD COLLEGE. Vol. LII. No. 13. REPORTS OX THE SCIENTIFIC RESULTS OF THE EXPEDITION TO THE EASTERN TROPICAL PACIFIC, IN CHARGE OF ALEXANDER AGASS1Z, BY THE U. S. FISH COMMISSION STEAMER "ALBATROSS," FROM L. M. OCTOBER, 1904, TO MARCH, 1905, LIEUT. COMMANDER GARRETT, U. S. N., COMMANDING. XX. MUTATIONS IN CERATIUM. By Charles Atwood Kofoid. With Four Plates. U. S. Fish [Published by Permission of George M. Bowers, Commissioner.] CAMBRIDGE, MASS., U.S.A.: PRINTED FOR THE MUSEUM. September, 1909. No. 13. — Reports of the Scientific Results of the Expedition to the Eastern Tropical Pacific, in charge of Alexander Agassiz, hy the U. S. Fish Commission Steamer "Albatross" from October, 1904, to March, 1905, Lieut. Commander L. M. Garrett. U. S. N., commanding. XX. Mutations in Ceratium. By Charles Atwood Kofoid. CONTENTS. Normal schizogony in Ceratium . 213 resolution of the C. tripos Division of ancestral skeleton . 214 skeleton 226 Formation of new skeletal The mutation between Ceratium parts 214 californiense and C. ostenfeldi 227 Similarity of normal schizonts Evidences of genuineness and in chain . 215 completeness 228 The genus Ceratium 217 Earlier observations on mutations Tripoceratium, subgen. nov. 218 in Protista 229 Macroceratium, subgen. nov. 218 Mutations in Diatoms .... 229 Biceratium Vanhoffen . 218 Mutations in Destnids .... 232 Amphiceratium Vanhoffen . 219 Mutations in Ciliates .... 232 Poroceratium Vanhoffen . 219 Mutations in Ceratium . 233 The mutation of Ceratium tripos Significance of the phenomenon . 235 to C. californiense .... 220 Unknown factors 236 Chronology and nomenclature Seasonal polymorphism (Gran of skeletal parts of chain . 220 and Lohmann) 237 Genuineness of the chain . 221 Gamete hypothesis 244 Completeness of the chain . 223 Degeneration or atavism hy- Evidence of mutation .... 224 pothesis 245 Progressive perfection of the Mutation hypothesis .... 247 mutant ........ 225 Bibliography 253 Significance of autotomy and Explanation of Plates Normal Schizogony in Ceratium. Throughout the genus Ceratium asexual reproduction occurs, in so far as is known, exclusively by schizogony. Multiple spore formation such as is seen in some other genera of diuoflagellates, as for example 214 bulletin: museum of comparative zoology. This takes the in Pyrophacus, is, as yet, entirely unknown. schizogony form of an oblique fission of the entire organism whereby not only the nucleus and cell plasma are divided but the parental skeleton as well. Division of Ancestral Skeleton. This skeleton is made up of a definite number of plates with a typical arrangement throughout all the species of the genus. It is parted at schizogony along existing sutures between the plates by the fission plane which is oblique to the major axis, passing at an angle of approximately 45° from the right anterior shoulder of the midbody to the left posterior region at the outer side of the base of the left antapical horn. By this process the ancestral skeleton is parted (see plates 1 and 2) so that the anterior schizont receives apical plates 1—4', precingulars 1" and 2", the two girdle plates between the proximal end of the girdle and a point near the middorsal line, and postcingular plates l'"-3'", in all 9 plates together with the proximal half of the girdle and anterior moiety of the so-called ventral plate. The posterior schizont receives precingulars 3"-4", the two girdle plates between its middorsal gap and its distal end, postcingulars 4'" and 5'" and antapicals 1"" and 2""; in all 6 plates, the " distal half of the girdle and the posterior moiety of the ventral plate." The ventral plate, as Lauterborn (1895) has shown, is divided between the two schizonts by a more or less oblique line, which passes from the at flagellar pore at the proximal end of the girdle to the attachment area its distal end. The position of the fission plane with reference to the skeletal plates was correctly given by Biitschli (1885) and Bergh (1886). but the number and position of the plates are not completely or correctly given by either author. The plates composing the skeleton and the nomenclature here used were described by me in a recent paper (1907 b). Formation of Neiv Skeletal Parts. As the schizonts diverge after nuclear division, their exposed plasma adjacent to the fission plane is moulded into the form of the completed epitheca and hypotheca and is coincidently reclothed with a thin hyaline pellicle, which in a short time shows the pores and arrangement of suture lines and plates characteristic of the species. The newly formed skeletal parts, as I have shown elsewhere (1908), take on the facies of the pa- rental if the skeleton was of a coarse-ribbed individual ; that is, parental and rugose type or of a more delicate and hyaline cast, the newly formed plates of the daughter schizont are speedily thickened and their surface kofoid: mutations in ceratium. 215 diversified to a degree corresponding to that of the parental skeleton by a sort of compensatory growth. The whole process is a relatively rapid one, with the exception that the prolongation of the apical horn to the full length normal to the isolated individual is often delayed as in all the individuals, save the anterior one only, in a chain of C. vultur shown in plate 4, fig. 7.' The result of this normal process of schizogony is the formation of schizonts which are, in all essential details, of similar form and structure. An illustration of this phenomenon is seen in this chain of C. vultur, where a series of schizonts of at least the fifth generation are seen still in chain. All exhibit the same form of midbody, essentially similar spread of horns with like major flexures near their bases.