ait i tegutan Tee etstie tage Weitvrd Ih y byte atin alae eu yee whet cl BRGh ds Why 9% hiiri n adaveyen amin ear ne py Le hee ye: r nd * e Liat pi peta ants tghan lacs al teh w zeae faded raneedebgne rab sat eae ; Lee tal niet : oe . dnpaeteet ied ona pitt Ney ates ‘, > $s r Wekee neta acral rt Vigaere en are " aged * vi ay i aah wh Fe ct ths dp (i i AN bs , oe Manat el pra ha eclae tee one vat : oe ae aes alintesersigia 1) Pere Merny ee eats gion ateh Dogger asp niet raterteDe Le cat cae 1 oie Sinehen [etabha thal m iy a ben ene! 1 F peo Re Te kcennen eee fate bie a rhe nafs ork RMS, “7 “ rod y Sahat) mor} + « po by pate rants SF : ited pet Ge oe a oat Popes ie Nest! ‘ Cpe base ae ens ped ays Ob City ce tips dorian eins seh nA Lyng cr inee ie hae Mite ston cane naan oa 4} Lied eis ot herp a " ald tei aie atabeaaal ed ent tta ah sensi is Hee it ues (22 sean at aA Hel Sst Laare Hat i i y sou aay? wo) na ott hips fs Ru i rice ‘ae Lands aces ALBERT R. MANN LIBRARY New York STATE COLLEGES OF AGRICULTURE AND HOME ECONOMICS AT CORNELL UNIVERSITY Exuviation, autotomy and regeneration in Cornell University Library The original of this book is in the Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924003398595 UNIVERSITY OF CALIFORNIA PUBLICATIONS OTN rae : ZOOLOGY — Vol. 4, Nos. 6 and 7,° pp. 345-393, text-figures 33. April 22, 1908 _ CONTRIBUTIONS FROM THE ae . : OF THE: MARINE BIOLOGICAL ASSOCIATION OF SAN DIEGO - _XXI (EXUVIATION, AUTOTOMY AND REGEN- ERATION IN CERATIUM, Sie BY 2 CHARLES ATWOOD KOFOID. x - NOTES. ON SOME OBSCURE SPECIES OF CERATIUM BY CHARLES ATWOOD KOFOID, BERKELEY THE UNIVERSITY PRESS UNIVERSITY OF CALIFORNIA PUBLICATIONS Note.—The University of California Publications are offered in exchange for the publications of learned societies and institutions, universities and libraries. 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IBC VSISY icteric tole dey Witte lle i ea i ou lh Ny Occurrence in Dinoflagellata Relation to schizogony With the compliments of Charles Atwood Kofoid Zoological Laboratory University of California: © vrs sue eisliabe suits 360 Berkeley, Calif. 361 - Ue UIOULY CMATACTET OT AUTOTOMY -......... ee eee ee cc eects 364 Location of planes of antotomy 2.0.0.0... ccc cceeeete eect ete 373 Significance of autotomy ............... . 874 Relation to specific gravity... cecccecececcseeeeetecsstetsceetteeeeeeeneeneeee 374 Relation: to specific surface. weve es. i yt ass ashen beens 374 Regeneration 10 Cena cwums ..istcczcusestiditaccesedea iets sant udes wane ite onmyeympenccucenssete 377 AEGON SCDIZO BONY? (ace: occsx eve ceccnin woth clerics enon aueldar Gocetar taht aetna es 377 Regeneration after autotomy —....00.- 0.0. . 877 Regenerative growth independent of autotomy .......000.0.020ccee ee 379 Regulatory nature of regeneration of the horns ....0000000ccecceeeeeeees 381 Significance of regeneration... 0.0 . 881 Summary Bibliography 346 University of California Publications in Zoology. [Vou 4 INTRODUCTION. In view of Ostwald’s (:03) able diseussion of the physical factors of the pelagic environment and Nathanson’s ( :06) recent suveestive presentation of the phenomenon of vertical cireulation in relation to the problems of plankton production, added interest attaches to all structural modifications and adaptations of the organisms constituting the plankton. New meaning and signifi- cance appear in characters which have lony eseaped notice or have been regarded as only additional instances of that wonderful variety of form and wide range of variation within the species which pelagic organisms are wont to exhibit. In the present paper certain structural features in the skeletal parts of Ceratium giving evidence of changes of functional sig- nificance are described and these changes are correlated with the problem of flotation as modified by the vertical distribution of temperatures and the possibilities of vertical circulation of ocean- ie waters. The genus Cvrativm is noteworthy amone pelagic unicellular organisms for the length and tenuity of the processes or horns which extend from the central midbody containing the nucleus and the main mass of the evtoplasm. In eommon with the rest of the body they are sheathed within a porulate cellulose wall or exoskeleton. These processes form the sinvle apieal and the two (in a few cases, three or more) antapical horns whose position, length, structure and angles of divergence exhibit a most remark- able variety in the scores of species known in the genus. These horns provide, as I have elsewhere (:08) shown, a functional adaptation to flotation and to orientation upon sinking, of prime importance to the species. In the course of my examination of the Dinoflagellates of the plankton of the Pacifie off San Diego during the past seven years I have noted numerous instances of individuals with broken horns and many cases of reveneration, in the normal conditions attending the life of the various species in the pelagic habitat. It is the purpose of this paper to diseuss these phenomena and the related one of exuviation in normal eon- ditions of pelagic life, and inquire into their Significance, es- 1908] Hofoid—Eruviation and Autotomy in Ceratium. 347 pecially with reference to the problem of flotation as affected by the extent and volume of the exoskelton. The term ‘‘eedysis’’ or ‘‘cytecdysis’’ will be applied to the process of shedding the entire cell wall at one time and usually in a single piece, in two pieces or in a more or less intact condition. The removal of the wall, plate by plate or in groups of plates of small extent may, on the other hand, be designated as exuviation or ecytexuviation. In the first case the cell contents withdraw bodily from the theea, while in the other the cell wall is cast off in parts and with the resulting temporary combination of new and old skeletal parts on one individual. EcpyYsIs. 1. Occurrence in Dinoflagellata.—In many Dinoflagellates the whole theca is abandoned by the daughter schizonts after schizo- gony and an entirely new exoskeleton is formed by each of the two or more daughter cells or swarm spores, as for example in Pyrophacus horologicum (figs. 1 and 2). At times in those gen- era in which the parental theca is shed at fission the cell contents may escape from the theca as a Gymnodinium-like, naked spore without preceding division, as in Gonyaulaxr, Diplopsalis (fig. 3), Peridinium (fig. 4) and Glenodinium. Subsequently, without in- tervening division, an entirely new theca is regenerated to replace that lost by this total and simultaneous eecdysis. The thecal plates are usually not dispersed but remain adherent to one another after the escape of the cell contents. Confinement in a crowded plankton collection under conditions of high tempera- ture, more intense illumination than normal and considerable concentration of the products of plant and animal metabolism, induces spontaneously this total simultaneous ecdysis in many Dinoflagellates in the course of several hours after removal from the sea. It also appears to occur normally in the sea to a large extent in Gonyaular polyhedra which forms the patches of ‘‘red water’’ off the coast of Southern California in late summer. In these swarms the numbers of Gonyaulax and other Dinoflagellates are so great that the concentration of the products of metabolism must approach that of an ordinary plankton collection, thongh 348 University of California Publications in Zoology. [VoL 4 Fig. 1.—Lateral view of Pyrophacus horologicum with swarm spores. X 300. After Schiitt (’96). Fig. 2.—Ventral view of the same after release of swarm spores by opening the girdle suture. X 300. After Schiitt (’96). Fig. 3.—Diplopsalis lenticula after treatment with alkali, showing con- tents escaping through the opened girdle suture. X 430. After Schiitt (’95). Fig. 4.—Ventral view of Peridinium ovatum showing spreading of the apical plates and the escape of the cell contents through the apical pore. x 240. After Schiitt (’96). the other environmental conditions such as temperature are not greatly modified. It seems probable that one or more of the changed relations in matters of metabolism brought about by these conditions may induce this total exuviation even in the nor- mal habitat. 2. Relation to schizogony.—It is noteworthy that genera which most perfectly exhibit simultaneous ecdysis without at- tendant schizogony are, in the main, those which at fission and spore formation abandon entirely the parental theca. This is perhaps not a universal rule, for I have found in some species 1908) Kofoid—Exuviation and Autotomy in Ceratium. 349 of Gonyaulax unequivocal evidence of typical oblique fission of the theca in recent schizonts. In the genus Ceratiwm oblique fission of the theca or exoskeleton universally attends schizogony and the parental theca is shared by the daughter schizonts. More- over in this genus no instance of total ecdysis has been noted in any of the numerous collections of living and preserved plankton which I have examined, neither from the crowded swarms in the ‘‘red water’’ or in condensed plankton collections which have stood in the laboratory for several hours. Fission of the theca in schizogony and entire absence of total simultaneous ecdysis thus appear to be the rule in the genus Ceratium. The possibil- ity of the occurrence, however, of total ecdysis at the time of sexual reproduction must not be excluded. EXUVIATION. 1. Statement of the problem.—lt becomes, therefore, a mat- ter of interest to consider the formation of the cell wall and the method by which the ancestral theca is passed on in asexual reproduction and what means, if any, exist for ridding the organ- ism of the accumulating products of metabolism found in the cell wall, and of adapting these fixed skeletal structures to the chang- ing environmental conditions which affect profoundly the capac- ity of the organism for flotation and maintenance in its position within the zone of optimum illumination in the upper levels of the sea. 2. Structure of the cell wall.—It is not my purpose to discuss the details of this subject which has been elaborately worked out by Schiitt (795, ’99, and :00) but merely to call attention here to the facts pertinent to this discussion. The wall and its super- ficial modifications are formed of cellulose or of a substance close- ly allied to it, and the material is laid down on the periphery of the main mass of the cell plasma and its extensions in the apical and antapical horns. Its increase in thickness is brought about probably by appositional rather than intussceptional growth, cen- tripetally on the inner, and centrifugally on the outer face of the wall, but principally by the latter process. Access to the outer face of the wall is gained through the many pores which are dis- tributed in the wall in all regions, though more sparsely towards 350 University of California Publications in Zoology. [Vou 4 the ends of the horns and less abundantly on the thin ventral plate (figs. 5 and 6). The plasma streams out through these pores (Schiitt '99) in long filaments and may form an extramem- branous sheet on the outer face of the exoskeleton. Both faces ei Bt f : le -- 4" 3” Ae 4” 3” egies Fig. 5.—Ventral view of Ceratium eugrammum, an anterior schizont after recent division. X 913. Fig. 6.—Dorsal view of the same. Regenerated moiety of the theca shown without pores. X 913. Abbreviations—ap. p., apical pore; f. p., flagellar pore; fis. l., fission line; l. ant., left antapical; r. ant., right antapical; tr. f., transverse fur- row; v. pl., ventral plate; 1'-4', apical plates; 1-4", precingular plates; 1’”-5'", posteingular plates; 1” ”-2”", antapical plates. of the cellulose wall are thus accessible to action of the cytoplasm in deposition or solution of the material of the wall. The thickness of the wall and the extent of its surface differ- entiations in the form of lists, ribs, fins, and rugosities differ con- siderably in different species, ranging from the thin hyaline, 1908] Kofoid—Ezuviation and Autotomy in Ceratium. 351 structureless, minutely porulate type seen in C. trichoceros (fig. 16) to the thick-walled, much ribbed and coarsely porulate one exemplified in C. robustum and C. limulus. In the normal course of asexual reproduction the type of wall characteristic of the species is maintained by immediate and rapid regeneration of o8 o-¢t.-1, ant. Fig. 7—Ventral view of another individual after exuviation of part of the thecal plates. Senile theca with heavy sutures and pores. X 880. Fig. 8—Dorsal view of same. X 880. (For explanation of abbreviations, see under figures 5 and 6.) the new half of each skeleton at the time of schizogony. The differences between the newer and older thecal moieties of indi- viduals recently divided and still in chain are usually obliterated by assimilative regeneration before the separation of the schi- zonts. On the other hand, within the lhmits of each species there is a rather wide range of wall structure between the more delicate and the more robust habits, which appears to be correlated with environmental conditions especially those affecting flotation. Oc- easionally heavily armored individuals of a species are found 352 Universily of California Publications in Zoology. [VE 4 whose habit is strongly suggestive of a senile condition and whose cell wall is apparently thickened by the accretions of Jong-con- tinued growth. Obviously such structure must profoundly 4 ffect both metabolism and flotation, for it cuts down the access of light to the chromatophores of the cell on the one hand and on the other affects both specific gravity and specific surface. 3. Transfer of the ancestral theca im schizogony.—aAsexnal reproduction in Ceratinm as in most Dinoflagellates and the flag- ellates generally, is accomplished by binary fission, though the Fig. 9.—Dorsal view of Ceratium vultur, a form with short horns in chain showing compensatory character of newly formed thecal moieties, to wit, the two thecal halves hetween the dotted fission lines. The weight of the lines represents the relative thickness of the walls. x 220. possibility of multiple spore formation can not be excluded. In the binary fission of Ceratin, as has been shown in detail by Lauterborn (795) for C. hirwndinclla, and as may be seen in most recent schizonts (figs. 5 and 6), the plane of fission is not transverse but passes obliquely across the body from the right anterior to the left posterior margin, separatine the parental theca into two parts. The anterior part includes the apical horn and precingular plates 1” and 2” and posteingular plates 1’”, 2'” and 3’” with the left half of the virdle which is ineluded between the two series of plates. On the dorsal face the suture 1908] Kofoid—Exuviation and Autotomy in Ceratium. 353 line crosses the girdle near the mid-dorsal line (fig. 6) but on the ventral face Lauterborn figures it as passing along the anterior margin of the ventral plate at the base of the apicals and down to the flagellar pore along the right margin of precingular 1’” and thence through the longitudinal furrow along the right margin of postcingular 1’” to the postcingular suture. Its course is outlined by a dotted line in figures 4 and 5. The pos- terior schizont receives the remainder of the plates, precingulars 3” and 4”, posteingulars 4’” and 5’”, antapicals 1”” and 2” ” and the other half of the girdle plates as well as the ventral plate (Lauterborn ’95). The right and left antapical horns thus be- long to the posterior schizont, and the apical to the anterior one. At the completion of each schizogony the parental theca is shared in this manner between the two schizonts, each of which regenerates during the process the missing half of the thecal exoskeleton. In chain formation (figs. 9 and 10) which ensues when schizogony is rapidly repeated the two parts of the ancestral theca are found respectively upon the anterior and posterior schizonts of the chain. It is evident that these ancestral por- tions may continue to form a part of the armor of some two of the offspring for an indefinite time unless some other type of reproduction intervenes, such as spore formation or conjugation, in which the cell contents abandon permanently the thecal exo- skeleton of this vegetative period, or unless some modification of the usual physiological processes occurs by virtue of which the thecal wall is resolved or shed in whole or in part. 4. Assimilative regeneration of the theca in schizogony.—lIt might be supposed that these ancestral contributions could be de- tected readily by their senile characters, such as thickened wall, and excessive development of superficial ribs and lists and in- ereased depth of color, but this does not appear to be the case. In many instances of chain formation which I have observed among various species of this genus I have yet to find an instance in which the older and newer portions of the theeae of the an- terior and posterior schizonts of a chain showed any considerable difference in their structural characters suggestive of a senile 1I have elsewhere (:07) described the thecal plates of Ceratium and proposed the nomenclature here employed. [ Vou. 4 University of California Publications in Zoology. B04 ———— of Ceratium protuberans (Karsten) in chain Fig. 10.—Dorsal view x 100. 1908] Kofoid—Exuviation and Autotomy in Ceratiwm. 355 condition. This uniformity of skeletal facies is due to the com- pensatory or assimilative nature of the process of skeletal forma- tion on the newer parts. As a rule a schizont with a rugged, robust, rugose and heavily ribbed ancestral moiety regenerates the lacking part of the thecal wall of a corresponding facies. It is true that schizonts in process of division, or very recently di- vided, will often have the ancestral portion of the theca upon one side of the fission line of a heavy facies, and upon the other side the recently formed part of more or less delicate habit. Such a condition is, however, temporary and quickly disappears, for it is apparent in the members of a chain of schizonts only in those rare instances where two adjacent individuals have been observed during or immediately after division. The remainder of the chain will be in almost all instances of uniformly rugged or delicate habit (fig. 10) according to the facies of the species or local environmental conditions. Evidence at hand indicates that in marine species chain formation takes place in the course of a few hours in the night. The rapidity of division and of re- generation of the lacking skeletal moiety and the compensatory nature of regeneration serve to obliterate to a large extent the dis- tinetions between the skeletal parts of earlier and later forma- tion. We have in this phenomenon a type of compensatory reg- ulation which preserves in the new individuals the balance of skeletal parts and thus provides for normal locomotion and for orientation by gravity. 5. Occurrence of senile forms in Ceratium—lt seems quite probable that long periods of schizogony may prevail in the ma- rine species of this genus. Sexual reproduction and spore forma- tion are, as yet, wholly unknown in any marine forms. Zeder- bauer (:04 and :04a) has observed the former in C. hirundinella, a fresh water species, and spore formation among species in that habitat has long been known. If these types of reproduction occur, as they doubtless do, among the marine forms also, they are certainly elusive and possibly rare. Given a long continued period of schizogony accompanied by some degree of assimilative regeneration of the newly formed portions of the theca in the cases of those schizonts which carry respectively the anterior and posterior moieties of the primal 356 University of California Publications in Zoology. (Vou 4 ancestral theea, we find at onee a basis for senility of skeletal parts in Ceratium. The origin of this primal theca is as yet unknown, though it may well be supposed to have been formed after an as yet undiscovered (for marine species) phase of sexual reproduction or spore formation in which all parts of prior an- cestral thecae were abandoned. It seems probable, therefore, that heavily armored or senile individuals of the various species which are found in any extensive collection of marine plankton owe their origin to the slow accumulation of ccllulose on the older thecal moiety and to the accompanying assimilative regeneration which gives a correspondingly rugose or senile aspect to the more recently formed part of the theca, and thus to the whole organ- ism. It is obvious that the senility here described refers strictly only to the formed skeletal part of ancestral origin and does not apply to the other half of the skeleton or to the cell body. It is therefore a pseudo-senility. Actual senility of the whole organ- ism following upon a long-continued cessation of schizogony has not been detected by me, as such, though detached individuals of senile facies may, indeed, belong to that category. 6. Removal of wall by solution.—As before stated, total sim- ultaneous ecdysis which would at once rid the organism of its impeding armor has not been observed in Crralium. Two other possible methods of removal suggest themselves: partial exuvia- tion and the resolution of the wall by the enveloping plasma. No evidence of the latter method has been noted beyond the fact of local solution in autotomy of the horns. Obviously it would be difficult to detect, except by observation during the process. Furthermore, it is probable that if it occurs it would exhibit the samé regulatory correlation that is found in thecal formation and result in a reduction of all parts of the theea to a similar type or facies of wall and would, therefore, be difficult to detect. 7. Evidence of cruviation in Cerattiwn—The removal of the thecal wall by exuviation or progressive shedding of thecal plates has not been hitherto reported. It is, however, easily overlooked and the process may well be more general than the data in hand indicate. Evidence of this method of removal of a greatly thiek- ened ancestral wall, probably at the time of fission in this in- 1908] Kofoid—Exuviation and Autotomy in Ceratium. 357 stance, is to be found in figures 11 and 12. In a collection of plankton of semitropical contents taken off San Diego in July, 1905, there oceurred a Ceratium arcuatum (2?) which exhibited unequivocal evidence of recent exuviation. As will be seen in the figures the specimen is possibly the anterior schizont of a recent division. The posterior segment of the theca, separated from ap. Pp... = pes i Fig. 11.—Ventral view of Ceratium arcuatum (?) in process of exuvia- tion. X 375. Fig. 12.—Dorsal view of the same. X 375. After sketches by Miss Marie Griffiths. Specific identification is uncertain in the absence of the complete ant- apical horns. Precingulars 1” and 2” and post-cingulars 1’” and 2’” and adjacent girdle are senile plates. The others are all of recent formation. the anterior by a dotted line in the figures, was very thin-walled and bore all the signs of recent formation. The anterior segment on the other hand had certain plates with strongly marked senile characters while its other plates were of very recent origin, being in fact visible only as exceedingly thin films. The senile plates, four in number, including precingulars 1” and 2” and postcing- ulars 1’” and 2’”, together with those segments of the girdle plates which go to the anterior schizont in division, were ex- ceedingly thick-walled, with a rugose surface deeply pitted by 88 University of California Publications in Zoology. [ Vou. 4 well-developed pores. They did not merge gradually into the thin plates upon which they abutted but dropped olf abruptly at the suture lines. Their thickness was not less than five times that of the adjacent new plates. The thin-walled plates of the anterior schizont included the four apicals, 1-4’ and precingiuars 3” and 4” They were uniformly thin and hyaline and their pores were searcely visible. The plates of the apical series were least regenerated, and were, indeed, barely formed at the distal end of the apical horn. The condition of all three horns in this specimen was mdica- tive of their recent autotomy. In C arevafion in normal condi- tion (fig. 25) the antapicals are much longer than in this speei- men and have pointed closed tips. The apical is also normally of at least twice the length in this individual. In this specimen all three horns are abnormally short and the antapicals are abruptly truneated and open. The three horns are, moreover, roughly still in the normal proportions of the horns in arcuatum to which species this individual appears to belone. The autotomy of the two antapicals is here attended by a proportionate redue- tion in the leneth of the apical. The conditions here presented by this specimen unquestion- ably indicate a process of exuviation in which a thecal wall of senile character is in the process of being dropped off plate by plate and replaved by a new wall of delicate texture. The or- ganism does not abandon its old theea as do Gli nodinium and Gonyaular, but drops it off piece-meal. Of the fifteen main plates of the theca but four here remain of the old type. It may be significant in this specimen that all four of these plates belong to the anterior segment. It is thus possible that this exuviation attended schizogony and that the anterior sey- ment shed its plates and regenerated new ones of a type similar to those forming on the posterior sexment as a result of the for- mation after schizogony of new plates over the whole body, be- neath the old on the anterior segment as well as over the posterior segment. The formation of the new plates beneath the old on the anterior moiety would result in the release and falline apart of the superimposed old plates of the anterior secement. It seems. probable also that autotomy of the horns of a reenlative or com- 1908] Kofoid.—Exuviation and Autotomy in Ceratium. 359 pensatory character accompanied or preceded this process of exuviation in this individual. Another instance of progressive exuviation which is not, how- ever, accompanied by either autotomy or schizogony was noted in GC. eugrammum, in a collection taken July 1, 1905, from the surface off San Diego. Dorsal and ventral views of this speci- men are shown in figures 7 and 8. The right half of the theca is composed of delicate hyaline plates, in which the pores are scarcely visible. The left half, on the other hand, is made up of thick, deeply pitted plates. The line between the two contrasted areas is nearly longitudinal and does not follow the oblique fission line, as will be seen on comparison of the theca of this individual with one after normal fission shown in figures 5 and 6. The heavy portion of the exuviating individual contains most of the plates of the anterior moiety of a recent schizont. It lacks, however, apicals 1’ and 2’ and ineludes antapicals 1” ”.and 2” ” which belong to the posterior moiety. The hyaline portion of this exuviating individual, which represents approximately the right half of the theea, includes apicals 1’ and 2’ which belong to the anterior moiety and lacks antapicals 1”” and 2" It seems probable that the senile thecal wall in the right has been exuviated recently and replaced by the new hyaline wall. The distribution of senile plates in both moieties of the theca is conclusive evi- dence that normal schizogony has not occurred in conjunction with this instance of exuviation, but the possibility of an abnor- mally located fission plane is not necessarily excluded. No in- stance of abnormally located fission planes has been observed by me in any Dinoflagellate. A number of other instances of par- tial exuviation were noted in this same collection in C. gallicum, C.inflerum, and C. carriense, and have since been observed by me in these species in other collections. 8. Significance of exuviation.—It is obvious that the removal of the heavy senile wall makes possible a restoration of the normal conditions of illumination of the chromatophores and facilitates adjustment of the specific gravity and specifie surface to the en- vironmental factors governing flotation. In the collection of plankton in which this exuviating individual was found there was an unusual number of instances of autotomy of the horns in 360 University of California Publications in Zoology. [VO . the various species of Ceralian represented. The collection had a semi-tropical facies, including such species as C. trichaccros, GC gallicum and C. biceps. We find in this exuviation an apparent adaptation to changed conditions of flotation. This plankton of semi-tropical aspect may be brought to the San Diego region by occasional invasions of water from the south, possibly by north- ward extensions of the in-shore counter current which has been reported off Lower California.? There is also the possibility that plankton of the warmer surface waters may at times, if not con- stantly, sink to lower and colder levels. Organisms of the plank- ton drifting northward or sinking to lower levels are thus brought into regions of lower temperature with inereased molecular frie- tion which makes possible a reduction in specific surface. Such a reduction is brought about by the exuviation of the old theca with its lists and rugose surface and its replacement by the smoother new wall, and also by the dropping off of the outer ends of the antapical horns or of all three horns. NorMAL AUTOTOMY IN CERATIUM. Any observer of marine plankton will have his attention often called to the large number of individuals of Ceratium, especially of the longer-horned forms such as (’. biceps, and many species of the C. tripos and C. macroccros groups, in which the horns appear to have been broken off. These mutilations are in some cases plainly of the nature of accidental breakages such as might come to pass in the exigencies of life in surface waters or result from collisions and rough handling which these delicate organ- isms undergo in the course of collection in the plankton net and in subsequent treatment of the material. The frequency with which mutilated individuals were found and especially their abundance in certain collections led me to suspect that other agencies than mere accident were at work in causing this phe- nomena in most of the mutilated individuals. A careful exam- ination of accumulated data on this point indicates that autotomy of the horns is a normal phenomenon in Ceratium. ' for this conclusion are as follows: The reasons 2 See Quarterly Current Charts of the H Admiralty (97). ydrographie Department, British 1908] Kofoid.—Exuviation and Autotomy in Ceratium. 361 1. Its general occurrence.—Few collections from oceanic wat- ers off San Diego in which Ceratium is found fail to contain some instances of autotomy. It appears, moreover, in practically all of the long-horned species belonging to the C. tripos and C. ma- croceros groups as well as in the more aberrant forms such as C. Figs. 13-15.—Ventral views of Ceratium gallicum showing proportionate reduction of the horns in autotomy. X 220. reticulatum and C. clavipes. The examination of a considerable range of collections at San Diego has afforded me evidence that this mutilation is more common in certain species, notably in C. biceps, C. gallicum (figs. 13-15) and C. trichoceros (figs. 16-19), ' a bige F 4 362 University of California Publications in Zoology. [VO and appears occasionally in most of the species having elongated slender horns. I have observed it, for example, in (. longipes, C. iutermedium, C. protuberans (fig. 20), GC. macroceros, C. 0s- tenfeldi, GC. vultur, C. inflecum, C. carricnse, €. tripos, C. areua- tum (figs. 11, 12, 26), ©. sehrauki, ©. azoricium and (. helero- Figs. 16-19.—Ventral views of Ceratium trichoceros showing progressive and proportionate reduction of the antapical horns in autotomy. X 220. The form of the end of the horns after autotomy is shown under greater magnification in supplementary sketches in connection with figure 17. camptwm. It oceurs also in the long-horned members of the sub- genus Amphiceratium such as C. ertensum and C. biceps (figs. 21-24). It is, however, relatively rare among the species of the subgenus Biceratium such as C. furca, C. lincatum and C. eugram- mum, where the antapical horns, and the apical also as a rule, are relatively short and play a less important part in the economy of flotation than they do in the long-horned species of the sub- genera Euceratium and Amphiceratium. 1908] Kofoid—Ezuviation and Autotomy in Ceratiwm. 363 2. It is more frequently found in collections from deep water (50-100 fathoms) than in those from the surface. It is also more abundant in collections of tropical facies occurring at San Diego than it is in those made up of species of more northerly distribution. Not infrequently, especially in the winter of 1904, the plankton collections taken off San Diego were unusually rich in species characteristic of the warmer seas, and at such times the proportion of mutilated Ceratium was unusually large. Instances of autotomy of the horns of Ceratiwm occur also in surface collections made off San Diego. There is no evidence at hand to show whether these cases originate in these levels or are brought to the surface by the upwelling of colder water from lower levels a phenomenon known to occur along the California coast (see Holway ’06) or by the aspiration of water from lower sec. pl.’ Fig. 20.—Dorsal view (somewhat oblique) of Ceratium protuberans in the process of autotomy. X 360. Supplementary sketches indicate the form of the section planes. Abbreviations—chr., chromatophores; n., nucleus; sec. pl., section plane. levels in vortices formed between currents of tidal or oceanic nature flowing in opposite directions, as shown by Nathanson (706). 3. Evidence of autotomy.—(a) Formation of section planes. The horns are cut off by the circular clefts, often though not al- ways quite regular in form and transverse to the axis, which en- circle the horns and form (fig. 20) wide V-shaped troughs, wider 364 Universily of California Publications in Zoology. [von at the surface, and steeper on the proximal face, which sink into the substance of the wall and sever it upon all sides. The super- ficial location of the troughs suggests the agency of the extra- membranous plasma in bringing about a local resolution of the cellulose wall. I have found no indications of local solution on the inner face of the wall below the groove. There is no evidence of a withdrawal of the distal plasma from the outer part of the horn to the region proximal to the plane of section in individuals exhibiting the early phases of autotomy. Isolated horns found in the plankton with the proximal stump conforming to the section plane formed by autotomy, often contain a normal plasma core. The line of breakage formed by fracture is, on the other hand, usually an irregular ragged line often oblique to the axis of the horn. (b) Regulatory character of autotomy—One cannot fail to be impressed with the fact that a large proportion of the in- dividuals exhibiting mutilation of the horns have either (1) both antapicals, or (2) all three horns cut off. This appears far in excess of the proportion demanded by the chances of accidental breakage. For example in a collection taken eleven miles off Point Loma on January 12, 1905, from a depth of 60 fathoms, a large number of individuals exhibit mutilation and of the first thirty-five observed in searching material with a mechanical stage no less than twenty-nine had both antapicals cut off, and twenty- six of these also had the apical similarly foreshortencd. The occurrence of individuals in which one or two horns have undergone autotomy while the other two or the third are still in the process is not unusual. An instance of this sort is shown in figure 24 of C. biceps, in which the apical is short, possibly as a result of recent autotomy, and the left antapical is nearly sev- ered by two separate and distinct but adjacent section planes at a distance posterior to the girdle approximately proportional to the foreshortened apical horn. Such cases are suggestive of an approximation in the time of the autotomy of the two main horns of this species. With a view of determining the extent and character of the processes of autotomy and of regeneration in a typical collection from deep water I made an examination of the plankton taken 1908] Kofoid—Ezuviation and Autotomy in Ceratium. 365 with a No. 20 silk net, which presumably retains most of the small and short-horned forms of Ceratium, from a depth of nine- ty-six fathoms off San Diego, June 29, 1905. This catch was made by towing at this depth from a drifting boat for about 20 minutes. The net is in action, however, during both the descent to and ascent from this depth. The net presumably obtained a large proportion of its catch from lower levels but also filtered some water from the intervening and surface levels. Samples withdrawn from the collection were examined with the aid of a mechanical stage and all individuals of all species of Ceratium were recorded with reference to their approach to the norm of the species as observed generally in oceanic plankton off San Diego. The length of the horns was measured in trans- diameters of the midbody at the girdle of the individual under observation, and the extent of regeneration, if present, was re- corded for each of the horns in the same units. By this method the proportionate, compensatory, assimilative or regulatory char- acter of the two processes of autotomy and regeneration of the horns is expressed quantitatively. Since every individual was recorded all elements of personal selection are eliminated. The results are very striking in that they exhibit the extent to which autotomy and regeneration occurred within the limits between a depth of ninety-six fathoms and the surface and also the degree to which the processes of autotomy and regeneration are regulatory. The first 125 individuals of Ceratium were recorded as shown in the accompanying table. 366 University of California Publications in Zoology. [ Vou. 4 SPECIES OF CERATIUM. ‘ i tal Normal ee Pe ae tone ee oray oud arcuatum 0 5 0 0 5 axiale 0 1 0 0 1 azoricum 0 4 1 0 4 biceps 8 16 1 1 26 bucephalum 1 0 0 0 1 candelabrum 3 0 0 0 3 carriense 0 2 0 0 2 deflerum 0 1 0 1 2 gallicum 1 6 3 0 7 heterocamptum 2 0 0 0 2 inflecum 1 13 7 2 16 intermedium 1 12 i 0 14 lineatum 5 1 1 0 vd longipes 4 10 3 2 16 macroceros i. 0 0 0 1 protuberans 0 8 0 0 5 seta 1 0 0 0 1 tenuissimum 1 1 ih 0 £ teres ak 0 a 0 1 tripos 1 5 0 0 6 vultur 1 0 0 0 1 Total 32. 85 19 6 125 These belonged to 21 species, of which 15 were represented in part or wholly by normal individuals, that is by those in which neither autotomy nor regeneration, either with or without pre- ceding autotomy, was evident. In species of the C. tripos group autotomy is revealed by the opened tips. In species of the C. macroceros group, carriense, deflecum, intermedium, longipes, protuberans, tenwissimum and vultur, which normally have open tips, autotomy is only made evident when the arms are appreciab- ly shortened by the process. The detection of individuals in which autotomy had occurred in these species is therefore a mat- ter of judgment and liable to error or prejudice especially in cases approaching the norm of the species. My judgment as to the norm is based upon my impressions after some years of ex- perience in examination of these species and upon the records of many measurements and comparisons with many camera draw- ings. 1908] Kofoid—Exuviation and Autotomy in Ceratinm. 367 But 5 of the 21 species, to wit: candelabrum, heterocamptum, macroceros, seta and vultur were represented only by normal in- dividuals. This is of little significance except in the cases of C. bucephalum, C. candelabrum, C. heterocamptum and C. seta in which, according to my observations elsewhere, autotomy is relatively rare. It occurs very generally in C. macroceros and C. vultur. The total number of normal individuals was only 32 of the 125 or but 26%, all others showing either autotomy or re- generation or both. Of the 21 species, 14 or 67% showed autotomy. Those in which it was not recorded being C. bucephalum, C. candelabrum, C. heterocamptum, C. macroceros, C. seta, C. teres, and C. vultur. It has been seen by me, however, elsewhere in all these species, but is more frequent in those with open tips, C. macroceros and C. vultur. Of the 125 individuals 85 or 67% had undergone autotomy, and it was more abundant, moreover, in those species of most frequent occurrence. In the species represented by + or more individuals, C. arcuatum, C. biceps, C. gallicum, C. inflecum, C. intermedium, C. lineatum, C. longipes, C. protubcrans, and C. tripos, were included 102 of the 125 individuals. The number of these in which autotomy had oceurred was 79, or 77.4%. It is particularly frequent in C. intermedium and C. inflexum. Regeneration on the other hand was much less frequent, ap- pearing, after autotomy, in only 19 cases or 15% and without evidence of prior autotomy in but 6 cases or 5%. It is, perhaps, significant that 17 of the 25 instances of regeneration occur in three species C. gallicum, C. inflerum, and C. longipes, in all of which autotomy is very frequent. To test the matter of the proportionality of the horns of in- dividuals in which autotomy and regeneration or both have oc- curred I have taken the first fifty individuals found by the aid of the mechanical stage representing the following species, C. gallicum, C. inflecum, C. intermedium, C. longipes, C. carriense, C. arcuatum, and C. biceps, merely omitting all normal ones after the first. Measurements of the total lengths of the horns and of their regenerated portions, if any, are given in transdiameters at the girdle in the following table. 368 University of California Publications in Zoology. eee Length of regenerated horns Length of horns in transdiameters in transdiameters Species Apical Right Left Ratio | Apical Right Left C. gatticum! 4.8 3.8 4.5 12 0 0 0 C. gallicum 3.1 11 1.7 1.5 ty) 0 0 C. gallicum 5.4 41 5.8 1.3 ti 0.7 0.6 O. gallicurn 1.2 1. 11 11 0 0 0 C. galliewmt 7.2 4.5 5. si: 0 0 0 C. gallicum 4.6 Hie 3.5 1.2 1, 0.6 0.3 C. gallicum 1.2 ue LT 0.85 0 0 0 C. gallicum 2. O:7 1/2 1,7 0 is) 0 Cc. gallicum 1.4 3.7 4.6 18 12) 1.6 1.7 C. anflexun? 1.8 6.7 7.9 1.2 0 0.8 0.9 C. inflexum 4.1 8.5 3.3 Ls 0.9 1 Ie 1.2 C. inflerum 5.2 4.6 5.4 p ee 0.7 Le 14. C. inflexum 0.5 AT 2.2 1.3 0 0 0 C. inflexum® 0.9 5.2 6.5 1.2 0 0.3 0.3 C. inflexum’ 2.9 1:3 4.6 2.5 0 0 0 C inflerum 4. 3.2 4.3 1.3 0 OL 0.2 C. inflexwm 4.3 Be 3.8 1.03 0.9 0.9 1A C. inflexum 3.8 BS 3.4 0.9 0 @ 0 C. inflexum* 0.6 BT 6.7 12 0.6 0.8 Te C. infexum 2.6 4.8 4.8 i ie 0 Ase 1. ee ee 3.7% 2.8 - inflexum 4. 1.3 { 7 { 13 C. intermedium?® 3.8 3.2 3.6 poe GO 0 0 C intermedium 3.2 2.6 3.3 1.3 0 0.8 0.8 C. intermedium 2.2 223 oe I (¢) 0 0 C. intermedium 1.5 0.5 0.6 1:2 0 0 0 C'. intermedium® 0.8 123 2.4 1.8 0 0 0 C. intermedium 0.5 0.5, 0.7 12 0 0 0 C. intermedium 5.4 3.8 6.3 a eg 0 0 0 C. intermediun? 1:5 0.8 1.4 17 0 0 0 eae j 44 a 0.9 0 0 0 C. intermedium 2.3 { 28 3.7 ve C. intermediun? 1.8 5. 1.6 0.3 0 0 0 C. intermedium 232 1.8 2.3 1.3 i) 0 0 C. intermedium 1s 1.5 LS: I. 0 0 0 C. intermedium as 11 12 Li 0 0 0 C. longipes’ Bi 3. 3. Is 0 0 0 C. longipes? 4.5 3.8 4.1 LA 0.5 ‘0:2 0.3 C. longipes 3.5 1.9 2.8 Ld 0 0 0 C. longipes(?1) 4. 2.5 3. Le 0 0 i) C, longipes 0.4 0.3 0.3 1.0 0 0 0 C. longipes 1.2 0.6 0.8 1.3 0 0 0 C. longipes 0.4 OF 0.8 11, 0 0 0 CG. longipes 1.1 0.6 0.7 Lt 0 0 0 C. longipes 2. ha 1.6 b ab 0 0 0 C. longipes® 5.5 4.7 52 a ie f 0.6 0.8 a hes j C. earriense 1.6 1.4 17 1.2 0 0 0 C arcuatum OT , 0.6 0.8 1.3 0 0 0 C. biceps 23, 0.7 30. 48, 0 0 () C. biceps 14.1 0.8 hip Fe E 14, 0 0 0 C. biceps 19. 0.8 10.5 13. 0 0 0 GC. biceps 4.5 0.5 4.5 9. 0 ) 0 C. biceps 3. 0.5 25 5, 0 0 0 1Normal. 7? Regeneration without indication of autotomy. * Autotomy not regu- latory. 4 Two section planes at about 2.8. °'Three section planes at about 1.7. 1908] Kofoid.—Exuviation and Autotomy in Ceratium. 369 An examination of the details of this table brings out certain significant tendencies. These appear perhaps most clearly in C. gallicum. A presumably normal individual has the apical, right and left antapicals in the ratios of 4.8—3.8—4.5, in a second case 7.2—4.5—5.0. In the six cases of autotomy recorded the apical retains an excess in length in all but two instances and in both of these there was evidence of recent schizogony and active growth of the newly formed apical. It is also noticeable that in four cases a considerable shortening of the apical is attended by much foreshortened antapicals. In the two normal individuals included in the table the relative lengths of the right and left antapical are 1 to 1.2 and 1 to 1.1 respectively. The average for all records of this species in the tables is 1 to 1.25 and for the six which have undergone autotomy 1 to 1.27 (range .85 to 1.7). In all but one instance after autotomy or regeneration or both, the individuals of C. gallicum recorded in this table show the left horn slightly longer than the right. These processes are thus regulatory and tend to preserve the norm of the species. An examination of the data of C. inflerum vields somewhat similar conclusions. There are three instances (5, 6 and 10 of the list) in which the apical is noticeably disproportionate. One at least of these (10) is due to recent schizogony. In the other nine cases there is a tendency for a short apical to accompany short antapicals. In all but two instances (2 and 9) the left horn exceeds or equals the right in length, as in C. gallicum, and in about the same ratios, averaging 1.26 (or omitting the aberrant 6 the average becomes 1.15). The normal relation of longer left and shorter right horn thus prevails in all but two eases of the twelve. One of the two instances (12) of dispro- portionately long right horn presents significantly no less than three incipient section planes forming in the longer right horn at about 1.7 transdiameters from the midbody. The completion of this incipient autotomy would bring the ratio of the antapicals to 1.3, nearly the norm for the species. The other case (6) of disproportionate length of antapicals shows not the least trace of approaching regulatory autotomy. In both of these the defi- ciency of the left horn is slight. The ratio of the two horns after autotomy is in general thus approximately the same as that 370 University of California Publications in Zoology, (Vou 4 before the process. The first individual listed presents approxi- mately normal conditious and has an antapical ratio of 1.2. With two exceptions in the table the ratios after autotomy lir between 1 and 1.3 or including the two cases of short left horns, between 0.9 and 1.3. The two exceptions both have disproportionately long left horns, that is the right horn has undergone autotomy while the left retains its primitive length. In the main the data from C. tufle.rtan support the view that both autotomy and regeneration are regulatory in this species. The exceptions are such as might attend schizogony or slight de- partures from coincident autotomy of the horns. The data from C. tntcrmedium are of similar import though somewhat more aberrant. In the thirteen instances there are five (5, 7, 8, 9 and 10) marked cases of disproportionate horns, that is of non-regulatory or possibly partially completed auto- tomy. One of these (9) has already two section planes at 2.8 transdiameters which when completed would bring the antapical ratio to 1.3, approximately the norm of the species. The re- maining eight cases present antapical ratios, after autotomy ranging from 1 to 1.3. In ten individuals of C. longipes there occurred seven in- stances of autotomy, all of which leave antapical ratios which fall within the limits 1.0 and 1.4, and five of them within 1.0 and 1.2. Similar regulatory relations in autotomy of the an- tapicals exist in the single individuals of (. carricnse and C. arcuatum which are recorded in the table. In C. biceps the right horn is always relatively very small and plays but little part in the mass relations and form resist- ance which control orientation and locomotion. Its autotomy and regeneration are, however, of frequent occurrence but are, it seems, often independent of these processes in the other horns. Autotomy of this horn is very frequent, much more so than that of the other horns. In many collections most of the individuals of this species will have the right horn truncated, as though there had been autotomy and subsequent healing without regenerative extension to the slender tapering antapex of typical form. Nor- mal regeneration is, however, occasionally seen. As in other species so also in C. biceps there is a correlation in the autotomy 1908] Kofoid—Eruviation and Autotomy in Ceratium. 371 24 23 22 ai Figs. 21-23.—Ventral views of Ceratium biceps showing progressive and proportionate reduction in the apical and left antapical by autotomy. X 100. Fig. 24.—Ventral view of Ceratium biceps after autotomy of the apical horn, showing two section planes, one of which is oblique, forming near the base of the left antapical. > 100. 372 University of California Publications in Zoology. [Vou 4 of the horns. It is most apparent in the tendency toward a pro- portionate reduction of the large apical at the same time with the left antapical in autotomy. A very short apical is usually aecompanied by a very short left antapical. The ratios of the antapicals of C. biecps, owing to their normal disproportion, are subject to extreme variations (figs. 21-24) in comparison with those in species having two large antapicals. as shown in the table. The process of autotomy is thus of normal occurrence to a con- siderable extent in deep waters in a large number of species of Ceratium and is regulatory in character in the main. Not only is autotomy found concidently, as a rule, in both an- tapicals, but it usually preserves approximately their relative lengths. As I have elsewhere shown (:07) the right antapical is formed by plates 4’” and 5’” of the postcingular series, while the left is formed entirely by the two plates of the more distal antap- ical series. This fact lies at the basis of the general occurrence in many of the species of Ceratium of an inequality in the length of the antapicals. The right is usually shorter and its base is always nearer the girdle, while the left is longer and its base is farther removed giving to the organism a fundamental asymmetry. This disproportion of the antapicals is most apparent in the subgenus Biceratium, while in many species of the C. mucroceros group the horns are approximately equal, the inequality appearing only on careful measurement. In a few cases in the C. tripos group the right horn is the longer one, as frequently in C. schranki, and sometimes in C. arcuatum. These sustained proportions in the length of the two horns, and not infrequently in that of all the horns, are characteristic of the species and they are preserved in autotomy. An illustra- tion of this appears in @. gallicum (figs. 13-15), C. trichoceros (figs. 16-19), and C. biceps (figs. 21-24), of normal individuals and others which have recently undergone autotomy. The orien- tation of the organism in flotation and in locomotion is obviously profoundly affected by its form and proportions. The preserva- tion of the fundamental inequality of the antapical horns in au- totomy is thus regulatory in character and may indeed be con- 1908] Kofoid.—Exuviation and Autotomy in Ceratium. 373 trolled by factors analogous to, or the same as those that deter- mine the original inequality of the antapicals at the time of schizogony. The nucleus is often found near the flagellar pore to the left of the center of the midbody and thus nearer to the base of the longer left horn than to that of the shorter right one. The radius of nuclear activity may be one of the factors influenc- ing the inequality both in growth of the horns and in their sub- sequent autotomy and regeneration. A striking instance of this regulatory phase of autotomy of the antapicals appears in those species of Ceratiwm such as C. schranki in which the proportionate lengths of the antapicals are reversed, that is the right horn is the longer and the left is nor- mally the shorter one. This reversal of proportions is usually retained in these species after autotomy. In C. trichoceros the two horns are nearly equal and vary considerably so that either horn may be the longer. In figures 16 to 19 are shown respectively a normal individual and several after autotomy, in all of which the proportions of the antapicals are approximately maintained. The apical is also shortened by autotomy but the proportion of the horn removed is less than that dropped from the antapicals, and the ratios which the stump bears to the antapicals are less regular than those between the two antapicals themselves. The following table gives the lengths of the three horns: Ceratium trichoceros, length of horns in transdiameters. Apical from girdle right left 8.4 14. 13.7 3. 4.55 4.65 5.8 2.6 2.7 1.25 65 1. The location of the planes of autotomy is not a fixed one. In- deed, autotomy may be repeated in the same organism at levels successively nearer the base of the horns (figs. 20 and 24). It is found in different individuals at all levels from the very tip to the base of the horns. A series showing different levels at which autotomy occurs in C. trichoceros is found in figures 16 to 19, for C. gallicum in figures 13-15, and for C. biceps in figures 21-23. A much more complete series might be made for these or many 374 University of California Publications in Zoology. (Vou. 4 other species in which autotomy is prevalent. There is no uni- versal or eeneral tendency for autotomy to occur at any partic- ular point. Autotomy in, or near the region of major flexure of the posterior horns is in some of my material more frequent than that in other regions, but there is no definite zone of autotomy here. This wide range in levels at which autotomy appears is in itself strongly indicative that the autotomy is not due to an in- ternal localized structural weakness which renders the arms prone to break at given points, nor to mechanical strains of external origin resulting from impact and producing localized breakage of the arms as a result of the general form of the organism. Autotomy does not always occur in both antapicals, or in all three horns, coincidently, nor does it always preserve the relative lengths of the horns characteristic of the species, but the propor- tion of instances in which these phases of the process are not evi- dent is so small that they fall into the category of exceptions to a more general rule. 4. Significance of autotomy—The wide-spread occurrence of this phenomenon is suggestive that it is a normal physiological process subject to regulation in common with growth and regen- eration. It is obvious that the loss of the horns modifies the specific gravity of the organism only in the event of unequal dis- tribution of density of the thecal wall. Evidence upon this point is only indirect. The horns are usually thinner-walled than the midbody, especially in their distal portions. Empty thecae sink to deeper waters as all catches from deeper levels show. The specific gravity of empty thecae may be greater than that of the whole organism. Autotomy leaves the thicker and presumably denser parts of the theca upon the organism and in so far tends to increase its specific gravity, thus tending to sink it to lower levels or assisting it in retaining its position at a certain distance below the surface when temperatures are lowered. More patent still is the change in specific surface which must result from autotomy. This removes from the body the slender horns, those parts in which the number of units of surface to each unit of volume is greatest. By the process of autotomy the volume of the organism is reduced, but proportionately less than its surface. This results in a decrease in the specific surface and 1908] Kofoid—Exuviation and Autotomy in Ceratium. — 375 therefore of the resistance which the molecular friction of the water affords to the sinking of the body. Ostwald (:03) has defined specific surface as the ratio of absolute surface to absolute volume. Computation of the actual surface and volume of a normal individual of C. gallicum and of the horns beyond a plane of autotomy midway in their length gives the following results, when S and V represent respectively the surface and volume before autotomy and s and v the corre- sponding measurements of the horns beyond the plane of section. Ss S—s yr Pye OF 265 > 210.5. The decline in specific surface is thus about 20.5%. Applying this to Ostwald’s (:03) computations of the changes in molecular friction attendant upon changes in temperature we find that an increase of 20.5% in the molecular friction found in sea water at 20% would be equivalent to a drop in temperature of 7.43°. In other words, a normal (’. gallicum before autotomy floating in water at 20°, would, other things being equal, be equally adapted to flotation in water at 12.57" by the autotomy of its horns mid- way in their length. Without autotomy its specific surface upon the lowering of the temperature would be in excess of its needs and would tend to maintain the organism in levels nearer the surface when once it entered them. The cause of autotomy is not easily determined in view of the complex and largely unknown chemical] and physical factors in- volved. Nevertheless the data of its occurrence are sugeestive of the agency of certain of these factors, which may, moreover, be tested by experiment. Ccratium presents in its structure cer- tain conditions peculiar among unicellular organisms, namely that of three distally projected protoplasmic horns which secrete upon their surface a continuation of the cellulose wall of the mid- body. The synthetic processes of the cell go on only in the presence of the nucleus. The distance from the mucleus at which the metabolic processes involved in the secretion of cellulose can go on are possibly affected by temperature. Whether or not this results from the relation of temperature to the velocity of chem- ical reactions, we do not know. The facts are that in warmer waters the horns of practically all species are projected to a pro- 376 University of California Publications in Zoology. [ Vou. 4 portionately greater distance from the nucleus than they are in colder waters. The contrast in length of horns of Ceratium from tropical and arctic waters has been a matter of frequent comment (see Chun 02) and the principle of the correlation of the pro- cesses of pelagic organisms with the function of flotation has often been noted [see Wesenberg-Lund (:00) and Ostwald (:03)]. Temperature thus bears a definite relation to the distance from the nucleus to which the horns of Ceralium may extend. In high temperatures this distance is greater than at low ones. So also | | 25 Fig. 25.—Ventral view of a normal Ceratiwm arcuatum. X 155. Fig. 26.—Ventral view of another individual after distal autotomy of the tips of the antapicals. X 160. in the fully grown organism it may follow that the distance in the horn to which the normal processes of metabolism can be maintained is in a similar manner affected by.temperature. , Entz (1902)° and Zacharias (1906)?, along with typical (. faea and (. lineatum (the so-called C. furca var. baltica Moeb. nomen nudum), but in no case has it been accorded spe- cific recognition, exceptby Vanhoeffen (1897) who described it as Drceralium debile. In the course of my investigations in the Dinoflagellata® of the plankton , I Fig. 1—4. Dorsal views of thecae of Ceratiwm furca, C. lineatum, C. eugrammum and C. teres. I—IV, precingular plates. « 500. Original. 4 Bergh, R.S., Der Organismus der Cilioflagellaten. Eine phylogenetische Studie. Morphol. Jahrb. Bd. 7. S. 177—288, Taf. 12—14. 1881. 5 Hensen, V., Uber die Bestimmung des Planctons oder des im Meere trei- benden Materials an Pflanzen und Tieren; nebst Anhang. Fiinfter Ber. Komm, z. wiss. Unters. d. d. Meere. S. 1—208. Taf. 1—6, 1887. 6 Entz, G. jr, A Quarnero Peridinedi. Névénytani Kozlémenyek Bd. 1. p. 83—86. Taf. 1—6. 1904. 7 Zacharias, O., Uber Periodizitat, Variation und Verbreitung verschiedener Planctonwesen in siidlichen Meeren. Arch, Hydrobiol. u. Planktonkunde. Bd. 1. 8. 498—575, 23 Taf. 8 Vanhoeffen, E., Die Fauna und Flora Grénlands. Grénland Exp. d. Ges. f. Erdkde. Berlin 1891—1893. Bd. 2. 8S. 1—383. Taf. 1—8. 1897. 9 Kofoid, C. A., Dinoflagellata of the San Diego Region. III. Descriptions of new species. Univ. of Calif. Pubs. Zool. Vol. 3. p. 299—360. pls. 22—33. 27 of the Pacific from Alaska to San Diego I have found this species in a large number of collections and am convinced of its distinct- ness from both C. lineatum and C. furca, with neither of which it inter- grades, and that it is, in all probability, the form the Ehren berg re- cognized and must therefore be designated as C. ewgrammum (Ehrbg.). The accompanying figures give, for comparison, dorsal views of four species, three of which have been subject to great confusion in the 'faunistic literature of the group and the fourth (C. teres) has been re- rently described by me. . C. eugrammum is the smallest species in the genus. It has a rela- tively narrow midboy with steep lateral margins of the epitheca. Its ‘antapicals are straight, and usually not diverging, and the hypotheca is but little contracted between the girdle and the bases of the antapicals. It differs from C. furea in its smaller size, greater delimitation of apical Heer et apie, Divergence of margins Ratio to trans- Species cal horn to , of ep itheen from-per- Postobliquity Transdiameter ere : s ft cnn epitheca pendicular to plane al ‘ ude o ofgirdle midbody. gradually jright 14° (10°—18")) 490 (350609) | 35 (30—50) u [1:2,25 1,5—3) Coie | erred | lathtG ES A94 | sha ue es iis «4.4 (right 30° (24°37) i 24 : lineatum | delimited cs 38° (33° 429) 18°(15°—21°) | 58 (50—67) w |1:1,1(1—1,25) = 6 gg tright 28° (15°—279| 540.990 _oam| ox delimited 24°(22°— 27°); 25 (19—30) w |1:1,4(1,3—1,5 ugrammum ania left 26° (25°—31) ‘i PA he \ v9) C.teres | delimitea [rght20° 12° (6°—19%) | 37 (30—40) wu [1:1,5,1,3--1,8) be left 30° horn from midbody, shorter antapicals, marked linear striae and more delicate habit. From C. teres it differs in the more robust habit and presence of striae, in the straight, rather than convex, sides of epitheca and hypotheca and in the absence of distal contraction of the latter. It thus lacks entirely the broadly fusiform outline which C. teres presents. From C. lineatuin it differs in its narrower midbody and steeper slopes of the antero-lateral margins of the epitheca. It is evident that C. line- atum and C. eugrammum are closely related as shown by their form and surface markings. They differ however in one important structural character, viz: — the precingular plate (fig. 2 7V) which is present in C. lineatum but apparently not in C. eugrammum. The normal number of precingular plates in the genus Ceratium is three but in C. lineatum and C. furca in some individuals, at least, an additional suture line passes from the suture between the apical and precingular series to the girdle plate, spliting the right precingular into two parts. This accessory 28 suture line is optically similar to sutures other than that of the line of cell-division which is more heavily marked. The appended table of diagnostic char-iers based on measurments of a number of individuals will serve more ciearly to define the charac- ters of the species in question. Northern forms (Alaskan) are absolutely larger in dimensions of the midbody than southern (San Diego), but horns, especially the apical, tend to be relatively longer in the indivi- , duals from warmer waters. Both C. lineatwn and C. furca are common cosmopolitan species alike in neritic and oceanic plankton. C. eugrammum is likewise cos- mopolitan and C. /evcs bids fair to exhibit a similar range as it is wide- spread in Pacific waters. These two species are, however, both relati- vely rare, perhaps in part because of the fact that their small size permits them to slip through the mesh of the silk gauze used in plankton nets. A few filter catches which I have examined have not indicated any abundance of these two species equal to that of (. furca and C. line- atum. They are apparently not well established dominant species and perhaps belong in the category of less sturdy mutants from some member of the (. furca group. Berkeley, California, March 23, 1907. UNIVERSITY OF CALIFORNIA PUBLICATIONS~— CONTINUED) AMERICAN ARCHAEOLOGY AND ETHNOLOGY.—Continned. Vol. 6. No.1. The Ethno-Geography of the Pomo and Neighboring Indians, hae A. Barrett. Pages 332, Maps 2, February, 1908. Price, S25 No. 2. The-Geography-and Dialects of the Miwok Indians, oF In S, Ai, Barrett. Pages 36, Map 1, February, 1908. — one No. 3. On the Evidences of the Qecupation of Certain- Regions ‘ cove by the Miwok Indians, by A. Kroeber. Pages 12 | Pri é, _ __ February, 1908. j .50 Vol. 7. No.1. The Emeryville ae. by Max Uhle. Pages 106, _ Plates 12, June, 1907. Price, 1.25 No. 2. Recent lovestigations bearing on the Question of the Occurrence of Neocene Man in the Auriferous Gravels of the Sierra ae by William J. ee Pages 25, Plates 2, February, 1908. . 3 : 5 . Price, 35 ASTRONOMY.—VW. W. Campbell, Editor. (Lick ery Mt. Hamilton, Cal.) Publications of the Lick Observatory.—\Volumes I-V completed. Volumes VII and IX in progress. Volume VIII in press. No. 1, A Shor Method of Determining Orbits from Three Observations, by A. oO. Leuschner. No. 2. Elements of Asteroid 1900 GA, by A. ©. Leuschner and Adelaide = M. Hoce. No. 3. Preliminary Elements of Comet 1900 II’, by R. H. Curtiss and ; C. G. Dall. No. 1. Organization and History of the D. O. Mills Expedition to the Southern Hemisphere. No. 2. Introductory Account of the D. O. Milis Expedition. No. 3. Description of the Instruments and Methods of the D. O. Mills Expedition. Lick Observatory Bulletins.—Volumes I-III completed. Volume IV (in progress). BOTANY.—W. A. Setcheill. Editor. Price per volume $3.50. Volumes I (pp. 418), II ‘pp. 354 , completed. Volume III (in progress). Vol. 2:— No. 12. Cytological Studies in Cyanophyceae, bv Nathaniel Lyon Gardner. ° : z z : : a : : ‘ « Price, -§.00 No. 13. On a small Collection of Mosses from Alaska, by J. Cardot and T. Thériot . « Privé, 160. x 150. represents Vanhoeffen’s genus Amphiceratium, C. furca (Figs. 1, 2) his Biceratium, C. gravidum (Figs. 7, 8) his genus Poroceratium, and C. intermedium (Figs. 5, 6) his genus Ceratiwm sensu stricta, for which he selected as a representative species, C. labradoricum Schiitt (= C. arcticum Clap. et Lachm.). This is well represented by my figures of the closely related C. intermedium. The fact that the plates of these proposed genera are all identical is in my opinion an imperative reason for rejecting the proposed dis- memberment of the genus Ceratiwm. Since the pore which perforates the epitheca of C. gravidum is absent in the very closely related C. prae- longum and is subject to great variation in the degree of its development in C. gravidum, even to its suppression, I regard this structure as not affording a basis for the generic distinction of the genus Poroceratinm,. 183 The mere modifications in the form and proportions of plates, even though they result in the development or suppression of antapical horns, is not, in my opinion, an adequate ground for generic distinctions among the Dinoflagellates. If applied to Ceratium hirundinella, for example, it would become necessary to erect new genera for the three, four and five horned varieties or growth forms of this variable species! The unity of the genus Ceratium rests upon the well-defined character of the num- ber of its plates and their relations. Berkeley, June 7, 1907. Papers Cited. 1883—1887. Bitschli, O., Protozoa. II. Abt. Mastigophora. Bronns Klassen u. Ord. Bd. 1. p. 617—1097. Taf. 39—55. 1834. Ehrenberg, C. C., Dritter Beitrag zur Erkenntniss groBer Organisation in der Richtung des kleinsten Raumes. Abh. Kgl. Akad. d. Wiss. zu Berlin. 1883. S. 145—336. 11 Taf. 1905. Entz, G. jr.. Beitrage zur Kenntnis der Peridineen. Math.-naturwiss. Ber. aus Ungarn Bd. 20. p. 96—144. 6 Taf. 66 Fig. 1884. Klebs, G., Hin kleiner Beitrag zur Kenntnis der Peridineen. Bot. Zeit. Bd. 42. 8. 721—733, 737—745. Taf. 10. 1895. Schiitt, F., Die Peridineen. Ergebn. d. Plancton-Expedition. Bd. IV Ma. Teil. L 1708. 27 Taf. 1906. —— Peridiniales. Engler und Prantls Nat. Pflanzenfamilien. 1 Teil. Abt. b. S. 1—30. 43 Figg. 1883. Stein, Fr., Der Organismus der Infusionsthiere. III. Abth. I. Hilfte. Die Naturgeschichte der Arthrodelen Flagellaten. 30 S. 25 Taf. 1896. Vanhoeffen, E., Das Genus Ceratium. Zool. Anz. Bd. 19. 8. 1883134. (Sonderabdruck aus dem »Zoologischen Anzeiger« Bd. XXXII. Nr. 1 vom 23. Juli 1907.) On Ceratium eugrammum and its related species. By Prof. Ch. A. Kofoid, Zoological Laboratory, Univ. of California Berkeley. cs (With 4 figures.) In 1859 Ehrenberg' described asmall species of Ceratiwm, related to C. lineatum, as Peridinium eugrammum but did not figure it until 1873 2 in a paper whose title failed to suggest its contents. This paper is not cited in any of the earlier or more recent bibliographies of the Dinofta- gellata except indirectly in Biitschlis Tierreich monograph. Stein (1883) cites this species in his monograph as a synonym of C. furca, a view acquiesced in there after by all other investigators. This species of Ehrenberg has reappeared in subsequent literature in the figures 1 Ehrenberg, 0. G, Uber das Leuchten und iiber neue mikroskopische Leuchtthiere des Mittelmeeres. Monatsber. k. preuB. Akad. Wissensch. Berlin1859. 8. 727—738, 791—793. : 2 Ehrenberg, C.G., Die das Funkeln und Aufblitzen des Mittelmeeres be- wirkenden unsichtbar kleinen Lebensformen. Festschrift zur Feier d. 100jahrigen Bestehens d. Ges. naturforsch. Freunde in Berlin 1873. p. 1—4, 1 Taf. 3 Stein, F., Der Organismus der Infusionstiere. III. Abt. 2. Hilfte. Die Naturgeschichte der Arthrodelen Flagellaten. 30S. 25 Taf. 1883. at } PENA a at ath ee rear ate Eb ait ee iictag ei " 4 i b yet hanger giei Sri Thebes ln? Sse tine & _ bing ean, bse Hy mri ins re Ba ae s set Patent ! sitchin Samat 3; tl at = plymeli nb ef a reece ye cy or aes ea fy ite ae © ms ts sin cities kl \ EE eis ’ | Aye v6 + ; bh ah de bd iat i a ame ket Hey Dag OT, Mea ttittepaed cm tae ricer o ilgeyiet fe rah tht op oF Lb abn in 8 PY, a If i mat aol Laat iat we ‘eyiw! | nt fae! Jaga ywovitis (aieae ot pel fat pbebol tis sue ih rn 4 D Boi S Bere iman ony br) ana ca Egan y Wats a gl tit Piatowe ate 9 ¥ Bylot ite ; reaey ap fal pA mip ieie Uf bs at haut 2 pay tee Rata, ; : 4 i rere + 8 weir plea a in Leu in f ie i, a4! Daten tt ei sia i id a vebrintay’, brant ah AP eT ah tre “4 ! gto Pissed te re i 4% er nee iti!