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UNIVKUMTY, ITHACA, N.Y. tFrom the Proceedings of the Ainerii-an Association for O^e Advancement of Science, Detroit Sleeting, Angnst, 1676. u SALEM, MASS. IfRIN'TKD AT THK SALKM PRK88. ■.■^:^;\'/ ■ 1876. For sale by the Naturalists' Agency, Salem, Maes. Pbice 50 Ct8. \ /' A V h ff .tdH^ ,^t V I CONTENTS. FA»a I. The respiratory actions of Amla and Lepidosteus. 151 II. The transformatl< ms of the tall of the gar-pike Lepldosteus. 158 III. The transformations of the pectoral flns of Amla and Lepidosteus 1^* IV. The brains of Amla, Lepldosteus, Aclpensor and Polyodon. 168 . . 189 \ -^■««««ysi.i^-y^^->' <:^^s^. -■^i^^lfttimm #st4J^^Mjf ,_- -^ i^im ^^ [ *.., —.* V J0 It _V^,_.,ir,, '?B#«'i- B. NATURAL HISTORY. »t .iff" Notes on tiik North Amkkicam Ganoids, Amia, Lkp:do9TEU8, ACII KNSKK AND ToLYODON. Hy IJUIIT G. WiLDEH, Of Itlmca, N. Y. (With three plutci.) > I. — The respiuatory actions ov Amia and Leimdosteus. The respirntory uctions of Lepidosteus liavo been iloscribed by Prof. L. Agivssiz and by Prof. Pocy. Tlie observations of the latter (27)' arc reproduced by Dnmcril (4, II, 30G). Prof. A See Hat of works referred to, at the end of this paper. The firs'; flgnre desig- nates Uie number of the work outhe list; the last, the page; themiddle, when it occurs, the volume. h 152 B. HATUHAL IIISTOHT. . lonfTth of tho Jaw, made it impoHsil.Io to dotormino whether this Ina8,„„ch, however, as tho exhalation oouhl bo ns well accomp. I'Hl.cl at any depth, tho uniform approach of tho gars to Z «urn.co goe« to show that air is taken in as well as ,iv!n out More sat, (uctory observations npon this point were m..lo"»non «c ult a„.l nn,„iured individnals of the .nu.I-,Lh, ArrJa, win , ^ko I^p.lo.eu.h.,. a very cellnlar an.l vasonlar air-blad.lor with arce au-dnct, and npon tho respiratory actions of .*|uch noil . Z! been published so far as I am aware. ° Amia seoms to prefer the darker parts of tho nqnarinm and to roma,n a ornear tho bottom, but like Lrpi.osteusl co Ito tho surface at .ntervals to breathe. One or two very largo b I ,^es of jr^e^r. '""""" -' - — '. -0 losserr: twn?i',' "n ?? '"'■''''' '•'' '"''^■^'"^"* «'■ ^''« J-^^" ^^^'"cd to be two-fold, first to permit tho escape of air, an.l second to take in a The following method was adopted for determining this point. lie fish was gradually accuslon.ed to the contact of tho Id gen ly en.brac ng the body at about tho middle. After a ti e would sw.m slowly in the tank with no apparent agitation o a count of tho contact, and como to tho surface at the usual into va s to discharge a bubble of air. an^ft-o'^at'l" ";"\P^!Pr'' ^he Ash was permitted to move to .Z,Tr ""' ""'"'"' """^ "'^«'' ^ ^^^ not ve y violent to'rs:tcr '^ ''"''' ^™'^^' ^ ^^'^^ '^'^^^ «^ «^^ -^'^'^ -« J,ih',"' 'f'''''" """"^ "^^ '^ '■'^""■^^^ ^« ™«y «"PP08e that it wo. Id have boon content. On tho contrary, after a second or two 01 lu.et (perhaps resulting from the habit of being satisfied after ' tho respuatory action), tho fish became n^oro and" more une^ y a 1 and finally escaped from the hand. It rose at once to the surface, and, wUhont emHting any bubble whatever, opened tkejat^ widely and apparently gulped in a large quantity of air. lluZ M3. _ .'0. -€» .%.'^LM. J— .-*i^ ??;•."*•♦« '-I-j.^ \ iiino whctlicr tliia as well UH of ex- I ns wol! n<'c'omp- tlio gars to the s given out. were mmlo upon imia, wliifli, like liuldor with large licli iiotliiiig 1ms nqimrium nnd to ) it comes to the large bubbles of OHIO lesser ones ■8 scemerl to be Jntl to take in a ted that I could ing this point, ct of the hand, After a time it agitation on ac- i usual intervals ted to move to but prevented ot very violent ' air which rose nppose that it second or two satisfied after more uneasy ; lashed with its it once to the pened the jaws 'air. It then B. MATURAI. IIISTOnr, descended and remained quiet for the usual interval. This exper- iment was several times repeated, always with the same result. There seems no doubt from the above, that with Amia there Is a true inspiration as well as expiration of air. The same may be considered [)robable though not yet proved, with Ltpidosteua. The escaping air should be chemically examined. But there can be little doubt that in these two genera, in Poh/pferua, and in the Dipnoans, all having cellular and vascular air-bladders, there is effected an interchange of oxygen and carbonic acid, as in the lungs of aerial Vertebrates. Amia and Lepidoateua have no spiracle and it is small in Polyp- terxia. The three genera have the space between the rami of the lower jaw occupied (by plates or folds of skin with underlying muscle) so as to better prevent the egress of air than would be the case with most Teleosts. But, as already stated, some air escapes from the opercular orifice of Amia and Lepidoateua after th. llsh has descended, and while, probably, the air is being forced back- ward so as to enter the air-duct. Amia and Lepidoateua were observed to perform the acts of respiration above described more frequently when the water wag foul or had not been changed. It was noticeable that they survived removal from the water for a much longer time than Acipenaer or Polyodon, whose air-bladders are simple and but slightly vascular. II. ^ The TKANSF0RMATI0N8 OF THE TAIL (»F THE GAR-IMKE, Lepi' doateua. That the tail of the young Lepidoateua is unlike that of the adult has been observed by Prof. Louis Agassiz. But although he repeatedly called attention to the transformation, little notice has been taken of it ; it is not mentioned in any systematic work in the English language. This neglect may have been due partly to the absence of figures from Prof. Agassiz's descriptions, and partly to their brief and, to some extent, contradictory nature. Tlie observations of Prof. Agassiz are here reproduced. "Zadock Thompson has described a young specimen under the name of Lepidoateua lineatua. I have ascertained, by a scries of specimens, that the detached lobe formed by the upper 154 B. NATURAL BISTORT. a distinct lobe, h!ZZ 't m ''''"'"'*' '"'•"'" "'« '«>^«r a •ncbrane aWs;„:\r^:,::;^l:;ro;e'. "'^ Pectora.s consist of "The joiing gar-pifcg are rem«ik»hl. .. embryological clmraotcr,. The Zt !^ ^ possessing certain pralongatlon of .l,e vcrtebj ttal ^^'T'" "' '"'" '' "<' n>cnt, distinct from tl,e ca", 1^1 J, r"!""" "' " "'"•>■ "'«- times a vibratory motioMnvll nta'rv 1 '^""' "'""""'J ""<' " .ot^n, or tbe^^ i.se,r.:ii':::r sir:Cs" •' '""- "- ^n. .ai. an, „. ,, ^^^rirX- : - passage «r,t '>'-o.r'i::'i7LVlZZS2 " '" ''" ■rtre'iS'i",'' ""''"""'' "*" »'"th re™'""'""' place be,„.tbl extrlit,;f tbe eSr"aT„ r ™"™ """'" '" anal, and tile vertebral ^J,.^..- ™, ""' <"'''"»'>. »s a second aiong the supe.o?btL:t^ira^;t:- J--'^^^ ^ sists until the fish is 200 ^9 ? . conformation per- length." (Agasl, ^^ 57 )' ^ '"""^*"^' "'°"* « '-*>-) in to be a very smill spedmen but wf ' I I '' "'^^^ '« «*«*«^ the figure and the sEessof 1 m ' ''f ^'"^ ^'•""^ '"^^ «'- ^^ 200- (about 8 inohe") "ng. "'"'' "^' P''^'^^'^'^ ^' '-«' My own observations relate to thp fnrm ^f n .... young, before it assumed the ehl . T ^' *^" '° ^''^ ^'^''^ manner of formation 7 be ea^^^^^^^^^^^^^ ^r''!? '^ ^^^"'^ ' ^'^^ Of the filamentary end of the bod- " <^isappearanee of the adult fish. ^ ' '*' representation in the tail the lower rays," I of Lepidoateus] m the lower as torals consist of • . they have e micklle line," sessing certain of these is the of a fleshy fila- ament] had at stiuct from the \'0S." fin is properly 3ohimn, a true the column." ^gassiz speaks ets, as in the the erroneous T rays." 'unded caudal iie caudal is 1 as a second Jtached lobe, rmation per- J inches) in Jriptions by at is stated I the size of ably at least in the very gassiz ; the lappearance 1 in the tail **.^■>?■^^ .i ._-. 1.:. B. NATURAL IlISTORT. 155 The material at my disposal is as follows :— A Young Lepidosteus brought to me in alcohol by Master Edward Steers (nephew of the late Prof. Evans of Cornell University), who took them from the Red River, near Shreveport, La.3 X . fl 1 The smallest of these is shown (enlarged 5 diameters) m tig. i. It is 18 millimeters (about f of an inch) long. The largest is 44™""" (about If inches) long. B Ten young Lepidosteus (probably L. osseus) obtained by me in the Illinois River, at Peoria, during July, 1876. These were kept alive by me and carefully watched for from three weeks to a few days each. The smallest is 63"""- (about two and a half inches) long; the largest is 300™™' (about twelve inches) long. C Numerous specimens and preparations of adult and partly grown L. osseus and L. platystomus in the Museum of the Cornell University. .. , The smallest Lepidosteus in my possession (it is apparently much smaller than any that have hitherto been examined) is 18'""- (a little less than three-fourths of an inch) in length. In figure 1 it is enlarged 5 diameters. Unlike most young specimens it is almost colorless.^ , „ i . The head is rather short and depressed like that of Polypterus. The eyes are large and dark. The nostrils are easily seen ; the anterior openings look upward and outward instead of downward and forward as in the adult. The branchiostegal membranes are separate as far forward as the transverse fold which exists in all Lepidosteus.* The ventral fins have not yet appeared. The pectorals are very large and* prominent, and consist of a central lobe with a thin border or fringe. The significance of this will be discussed here- after; see page 166. ,^ , ^u * A median fin extends from the middle of the length to the vent, .several of these were handed by me to the late Prof. AK""'- y"-;";'""''**^^ hlg failing health and pressing avocations prevented any examination Of them, and they have Ulen Sy Toan'od to me by Mr. Alex. Agassiz, Curator of tho Museum of Com- ''Tiws U Sr/ase with two small specimens aboutB-™ long, taken flrom the stomach of JsmM Lepido,teu,. They are probably newly batched gars, but are not capable "MthSS are reasons for regarding this fold as homologous with the hinder borderTf tlie guiar plate of Amia. But as this question Involves the homology of ■ome other parts now undetermined, I reserve it for another occasion. )iiii'iiii»'»»«ii|p«i>»»g(iiM»'W>* 156 B. NATURAL niSTOBT. and thence to the end of tho fnii a • -i - «s aiong the hinde 'third of t' ,oXZlZ ' xT^f •'" ^^■ deep and consists of a delicaf« rT^K ' ^" '^ *J"'*« numerous and slender ravs in cTol! '"' '"^P^*'^^ ^^ ^''y backward. ^ '^°'' apposition ; they incline slightly >lio«r a gradual .|,a„„|„„ „,°; . ' ^'"' '"Kef specimens m.y Infe? that n Z ^ ^f *!,r''' "'""''^ '*™- "• 2- M —a, „.:r:i ;tr srsr:^: They appear to be somewhat thiclcpr fho« tu^ of the fin, and darker fromr^L . I ^ surrounding parts Str'-'^' .an .e<,e„ea. r^^^XZ^^Z mens. It has no large ravs and i!! ™''*^'^ '° '^'g^r speci- fy possibly represer thrser„dlr;Tr;;"^ -ore probably the upper lobe of the audal fi?^ "S !? Z7:Z:J''' correspondence will be reLred L h^rtlr The spot (C) on the lower lobe of the caudal nf ti!! "^^^"f' dosteus is evidently a develoDins fi„ '''^, ''!"''*/. *>f ^^^ ^o^^g ^ei>t- of the primordial L. In the cent/e of thV.; f T '''' '''' dimlv seen four nr fi.. i '^® thickened space are and LokwaS Their atTT T '""""^ obliquely downward indicated by its ?h^kel?"^>!° ''' ""^'^ °^ *^« ^'^y »« ^Jk .*„.:jfc.i.. B. NATURAL HISTORY. 157 rnordial fin ex- This fin is quite hited by very I incline sJightJy I tliis specimen, fger specimens py. whence we P'ery acute. otonward incli. either nearly r. special altera- opposite each 'tejior to the funding parts n of pigment y the portion arge rays, or >rdial fin, are 'd hardly be larger speci- ntirely.5 jj ^cemus; but Undina and h6reaflter. ^oung Lepi. an the rest space are downward le body is ""gination. the tail of probably ted. ■Dgr skate as •l«e before The spociri. ; above described, represents, so far as, I am aware, the earliest known stage of Lepidoateus. But there can be no doubt that at a still earlier stage the tail was simple and undiffer- entiated like that of Amphioxus. A second very small specimen is no longer than the one above described, but seems to be more developed. It is darker colored ; the belly being almost black while the upper half of the body is browjiiiJh. The four median flns are indicated by decided though irregular blotches, and the rays of the infra-caudal are more dis- tinct. White longitudinal elevations show where the ventral fins ( Ve) are about to appear. The difference in the color of these two smallest specimens is very marked. The white one is apparently the younger although a trifle the longer. But it cannot be determined at present that the color is developed only after the attainment of a certain size or stage of growth. The specimen next figured (Fig. 2) presents the following fea- tures. Its length is 23"'"'- Its colors are darker than the one first described, but less decided than in the second small specimen re- ferred to. The ventral flns ( Ve) are little white buds opposite the anterior extremity of the primordial fin (1). This latter has changed but little. It seems rather thinner and its borders are ragged, as if in process of removal by both absorption and abrasion. In addition to the interruption for the vent, the primordial fin now presents three emarginations, as follows : — 1. About mid-way between the spots representing the dorsal and the supra-caudal fins. 2. Behind the spot representing the anal fin. 3. Between the primordial fin (3) on the lower border of the tail and the infra-caudal lobe, which now projects slightly and is supported by eight or ten rays split at their tips but reaching the border of the fin. In this specimen we see the beginning of the changes which are to result in the total disappearance of the tail proper and the taking of its place and oflSce by the greatly enlarged infra-caudal lobe. Passing over intermediate sizes in which the head is progres- sively lengthened, and the ventrals enlarged we come to the specimen represented in fig. 3. '^yff. t, iw miii ^i |i w * » -ate, tJio tliin Iflesliy central I'l seven raya. "lore nearly vliile the tail ■caudal lobe come wider, i'ament. It se from the 'inois liiver Idle of eye ; ament. tliose from 'erof the f caudal J's, that 2 body, while the base of the filament is crowded upward. There are now Ave pairs of fulcra, the liindermost of which extends back- ward as far as the point of separation between tlie filament and the lobe. Behind tliis point the filament is apparently undergoing structural degeneration and removal. It is thin, slender and ragged at the edges. But there is evidently considerable variation as to the period of this removal. For of two specimens about 190"""- in length, one has the filament equal to the lobe, and in the other it is but 3"""' shorter. Tlie largest specimen in which the filament is preserved, is about 800'"'"- long. The lobe projects IS"""'- beyond the filament. The free part of the latter is much attenuated, and, during life, was but feebly and occasionally employed. The tail of this specimen is shown in fig. 4. In imagination we may readily supply the stages intermediate between that last described and the tail as usually represented, where the free part of the filament has wholly disappeared, and its base, covered by the fulcra, seems to form only the upper border of the functional tail. Tliis latter, however, from a mor- phological point of view, is really an appendage of the filament. The movements of the filament have been well described by Agassiz. He, however (2), speaks of it as "involuntary." By this he may have meant only that, as with other very rapid vibra- tions, a separate volition is not required for each individual move- ment. In fact, during vibration, the filament is invisible. But the motion is not involuntary as is that of cilia or unstriped mus- cular fibres. For at times the filament is wholly at rest ; it may be elevated or depressed, curved strongly to the one side or to the other, and more or less rapidly vibrated in any of these posi- tions. The movenfent may be compared to that of the wings of most insects and of the humming-bird. Still more closely with that of the tail of Crotalusfi On each side of the cartilaginous rod, in its whole length, is a band of striated muscular fibre. It would be interesting to ascertain whether the nervous supply comes from the cord within the filament or from tbe permanent • Many of the Colubrida, nnder strong excitement, will vibrate tlie tail as does the rattlesnake. 4i. m *IIO B. NATURAL HISTOnT. „. portion of the cord anterior to the point of its separation from the infra-eaudal lobe. The representation of the filament in the adult tail. Agassiz' figure of the tail of Lepidoateus (5, tome II, tab. A), was prob- ably made from a dry preparation, and his description (tome I, part II, 23), does not mention any cartilaginous prolongation of the bony vertebral column. I am not aware of any other figures or description of the tail of Lepidosteus. Figure 5 represents (reduced i) the dissected tail of a medium Bized L. platystomus. It will be noted that the ouMine of the caudal fin (the infra-cau.lal lobe of the foregoing descriptions) is nearly though not quite symmetrical ; the lower rays being a little shorter than the uppermost. In the figures of Agassiz and Du-.n^ril the outline is much more oblique. This however, may be Jue in part to the fact that the upper rays are usually less separated than the lower, so as to cover less area than the lower. Probably too, there is specific variation in this respect. I am inclined to think also that the same species presents different characters at diff-erent ages. But for the determination of these questions a large number of individuals should be compared after their species have been ascertained. At present the taxonomy of Lepidoatetis is in a very confused state.' The outline of the base of the fin presents a double curve like an elongated letter /. The fulcra cover the anterior two-thirds of the dorsal border and three-fourths of the ventral border. Both series are closely attached to the uppermost and lowermost caudal ray respectively. These rays not only divide and subdivide like the fin rays of Malacopteri, but also consist of two lateral halves* which are often not exactly applied to each other, as seen in fig. 6. The lateral halves of the uppermost caudal ray are separated from each other excepting at their lower border,' and between them lies a tapering cartilaginous rod, whose upper surface is covered by the bases of the dorsal fulcra. The relation of parts i» L^*"^ '""f ** '""^ '"' """"y *"*'®'" American forms which are not readily obtainable ta large numbers by European naturalists; as, for instance, Ihelmerican Sturgeol the Petromyzontlda), and the tailed Batrachians. -"t-ncan sturgeous, rave of mplllil';"' "*^ ?"" Humphrey (8, 69) have called attention to the fact that the meSanTlZ'' TJ '""'"S f f '""'"" "" '» """"'Po-"! to a lateral factor of a wlee doub"; ' ""' '^"' '" ^'»"*'"«'» ">« «y« of *•>« ventral flna are like- "^^ i* • m.. ;wii,im*.!^-U- .r^ '.jmtm' 1^ — B. NATURAL HMTORT. 161 ration from the fail. Agassiz' » was prob- iHion (tome I, [olongation of other figures of a medium >uMine of the ascriptions) is l^eing a little is much more fact that the ""er, so as to aspect. lam 3nts different t'on of these mpaied after taxonomy of 'e curve like two-thirds of >r(ler. Both most caudal Mivide like eral halves' en in fig. 6. e separated id between surface is •n of parts ly obtalnnlile, m Stiirgeoua, fact that the «l8 It asono 1 factor of a lus aro like- Is seen in flg. 6, which represents a vertical section of the upper border of the tail about the middle of the series of fulcra. Posteriorly the rod may be traced to beneath the hindermost fulcra, this point corresponding nearly with the point of separa- tion of the filament and infra-caudal lobe in the young. Ante- riorly it descends gradually to become continuous with the hinder- most vertebra. The cartilaginous rod above described is called notochord by Huxley (7, 20). A cross-section, however, shows that it really represents the whole spinal axis, as seen in fig. 6. The noto- chord (IT) is surrounded below and on the sides by the cartilagi- nous and unsegmented basis of the vertebrae (CS) which, above, separates into two laminie enclosing the neural canal and the spinal cord (<> Cope (17) has proposed " isoceroal " for the Bame form of tail. But he applies this term to tiie eel (.Anguilla), in whicii, according to Uuxley (IS, 42), the arrangement is really heterocercal aa in most if not all other osseous flshes. Tlie whole subject, tiow- ever, needs a special revision by comparison of several stages of development of the tail in all forms of aquatic vertebrates. I >."•-. ,^ J — B. NATUUAI, iiisTonr. 163 •n of the upper camJul 'f Fianquo (lo) and »c adult Amia rcsem- 3ul inferring that it ^tions. AndlwoulU places of Amia, the ' .a^ -mmr •rr • -».^-^ ,■*>■■ B. NATURAL HISTOnT. 16A have their more or less accurate counterparts among various living and fossil Ganoids and Simrks.'^ Alo})iiiii has a long upper lobe (so-called).'* In Pohjndnn and some species oi Ar.lpvnuer and In most Sharks, the upper lobe is but little the longer ; in iMtnna the lower lobe nearly ei|ual8 the upper. I am not acquainted with any Ganoid or Selachian where tiin lower lobe is the longer, as in the sixth stage of LcpiiloHleus (Fig. 5).'* The last stage (7, fig. G), exists in Amla olone among living Ganoids, and, so far as I am aware, is not presented by any palae- ozoic forma ; their tails being either protocercal (as in Olyptolce- mu.t) or obviously heterocercal as in Pulceoniscus, etc. But among mcsozoic forms the amioid tail is not unusual ; and a series may easily be formed, as, for instance, of Lepirlotua, Meg- alnrun and Thviiianpa by which the truly heterocercal tail is appar- ently converted into the apparently homocercal form. Indeed the tail of Mpgalurua, as figured by Agassiz (5, tab. K, fig. 4), might almost be tauen for that of Amia.^'^ " Several (. 336), thinks " thoro is no positive roaaou for arranging the Mcga'.uri (whiuh he regards at Teleo^toi) with the Amiadie." 1 W-: '«"»«*f"?»*»^ .: ' 1 / 1C6 B. NATIIHAI, IIISTonr. ( ^ ' ! I I ( ! / Since I[iixloy(l5) \\m sliown tlin pioliahility tlmt tho tfills of most iC not all IVlcoHtci, iir« rcully Htrongly liclerofciciil, it i.s not (lilllcult to inm','ino n seric» l)y wliicli llie tiiii of AmUi nIiouIiI i)0- coino tlmt or one of tlio ClnpooiilN willi wliicli Ciivier iwid piiiccd It. Indeed tlicre ure CosHil VtwxwVU {ThriiMMqiH, Ax\)U\nrh\ini-hn»^ etc.) wlioso tailH ivie ivj)|)iirontly ns peirecliy lioniocorcal us tliosoof any ISalmu or Scomber, hut wiiicli, i»y anuioj^y, wo may snpposo to have luuMi, in tlio earlier 8tuj,'c« of dcvcioptnont, distinctly lictero- ccrcal, or, perliaps, ev»!n protoeercal. Bnt the transition is still i)etter illustrated l)y tlie ciianges wliieh occur in Gtutvrmteuit as described l)y Huxley (Ifl) and us lately seen l)y me in a Siluroid. For in the young Oastprontem the cartilaginous rod (called nolo- chord by Huxley) is not only strongly bent upward but also reaches the upper angle of the tail, nearly as in LppMostnm. Hut in tlie half.grown fish, by the growth of the (In rays the end of the notochord " no longer reaches, by a long way, to tlio posterior superior angle of the caudal tin ;" this is tho condition of things in Amid, It may be saiu, therefore, that the Teleostcan tail does not simply begin where the Ganoid tail leaves off, but actually overlaps it; the two earlier stages of the former being represented by the tails of LepidoHtcua and Amia, the latter genus, as luis been already stated, being regarded as the most telcosteoid of Ganoids. LiJtken has remarked (16, 332) that "in general an evident progress from the heterocercal to the so-called homocorcal or fun- like tail may be observed running parallel to the progress of tho g((ological epochs." The transformation of the tail of Lepidonteus so far ns already known, would have furnislied an embryological parallel to the structural and geological series ; while the earlier condition hero first described enables us to extend the comparison to the proto- cercal forms of which some are among the oldest known fishes and others, now living, are either tlie lowest of vertebrates or manifest such striking relations with other classes as to have received the name "generalized Ganoids." ill. — The transfoumations of the pectoral fins of Amia and Lepidosteus. Raflnesque" described a small gar-pike under the name Sarchi- >' Journ. ac. nat. «oI., PhUad., 1818, vol. I, part 11, p. 418. -^.^.^,^, r\.: ,mmr m-^mA.t^ ^"^^i^M .^; n. WATURAL niSTORT. 117 lily tlint tlio tnilM of It'lerowical, it U not I of Amia nIioiiIiI l)t>. Ill CiiviiT IiikJ pIlKJcd I'V'''. ^ iKpiihirhjindt «/», |f)iiioi!crc(il «« tlioso of >vc limy siii)|»oHc to |"t, distinctly lictero- '»y tlio clinngofl which y (15) and ua lately nils rod (called nolo- it upward hnt also M Lppithatum. \\y\\, niys the end of the ••^y, to the posterior condition of tiiingg tftil docs not simply ictiially overlaps it; •esentcd by tlie tails IS lias been nircady of Ganoids, general an evident Iioniocorcal or fan- the progress of the us 80 far ns already 3al parallel to the ilier condition here •ison to the proto- it known fishes and Jbrates or manifest ' have received the FINS OK Amia and the name Sarchi- % p. 418. run bccauNO the pectorals consisted of a memlirano rising (Voiu a fleshy lobe. Agassiz (9, 360 ; 8, 5R) has shown that tills form of pectoral la ciiaractoristic of the young Lvjiiiti)nteug. Dumorll (i, 320) rpiotos Agassiz' observations but makes no comment noon them. No other systematic work, so fur as I know, contains any rcferonco to the fact. Since Iluxloy (6, 24), has proposed a now sub-order of Ganoids, Crossopterygla, mainly "in consideration of the peculiar manner in wliicli the fin rays of tlio paired fins (tlio pectorals and usually tlio vcntrals) are arranged so as to form a fringe round a central lobe," it is desirable to ascertain whotlier the early stages of othor Ganoids exhibit similar features. This is certainly thn case witli all the young Lepidosteus above described, including the largest. Moreover, in any minute de- scription of the adult L. platyatomus, the pectoral fins would be distinguished from tho ventrals by the existence of a dccidod fleshy rounded lobe at their base. In the smallest gar (Fig. 1, P) the fringe forms little moro than one-third the wholo length of the fln. As tho flsh grows the lobe becomes rather longer and narrower, but the fringe increases so much more rapidly as to render the former comparatively incon- spicuous in the adult. The pectorals of Amia, even the adult, have a fleshy lobe. In the smallest specimen already alluded to, the length of the whole fln is 10""" and the basal lobe forms one-flfth of this, 2'""' So far as regards external form alone, both Amia and Lepidos- teus must be regarded as having lobatc or fVinged pectoral fins. But the significance of this fact depends largely upon two other considerations. 1. Is the structure of the fin identical with that of Polypteru» and the other forms included among the Crossop- terygia? 2. Is the lobe necessarily covered by scales? It is so covered in Polypterv.a and, as I infer, in the fossil genera. But I have not found scales upon the lobe in even the adult Amia and Lepidosteus, Since, however, all those forms, like the young Lepidosteus, were probably scaleless when young, it would seem that not much weight should be assigned to the lack of scales in the adult. ,N ,J. 0' jL^J^y ^«»«»^,^ m^ ■ LUtken makes no reference to the brain, and his characters seem to be in other re- spects defective. But (p. 336) he admits the possibility that Aiture discoveries max some day demonstrate to us unknown bonds. "^-mrw- .•s^-,»%'^--'^' B. NATURAL HI8T0RT. 169 fS, ACIPENSER AND zoologists respect- is Ganoids, and its r Vertebrates. To Miiller, including, us, Polypterus and lyodon), Amia was djoin the Siluroids, jrill (12) considers ey) and Dipnoans" atodus) exhibit so ven entitled to sab- ers the Dipnoi as a he Selachians as a ) goes to the other only the sturgeons icognize the group imits and relations sales, to the dermal celeton in general, [ the multivalvular lolly unknown, and fore, not at present into the discussion Granoids differ from he Selachians and the brain is more comparisons have lose of other fishes ho alludes (12) to 9 of the brain and rs seem to be in other re- Aiture discoveries maj i heart in other classes of Vertebrates," does not refer to any other feature than the optic chiasma already mentioned. Having reasons,«« other than those derived from the extreme diversity of conclusions already referred to, for beUevmg th«^ a Treful study of their brains will throw light upon the limits and c a smcation of Ganoids, I have this summer (1875) made numer- ous preparations of the brains of the four American genera ^m.a, . ZpLLs, Acipenser and Polyodon, ''^^'"'"iV V^^T^ other and with the figures and descriptions of Ganoid brains to which I have had access. Since, in comparison with the preparations, none of the pub- Ush^d figares and descriptions are wholly satisfactory, I here refer to them in detail. . , u • s= fi,of hw Apparently the earliest figure of a ganoid brain is that by Stfnn^us (32) of the sturgeon's brain. It seems to be a correct Representation, and fairly indicates the features which, according to the views I have reached, are characteristic of *he b-ns o^ ^ Ganoids. But no especial attention is drawn to them and the nomenclature of the two anterior pairs of lobes has not been ac- cept d by later authors. Starinius calls the first pair from which arise the olfactory nerves, the olfactory tubercles, and the second Zv which most authors call hemispheres (but which I believe to rspldllly developed portions of the thalami), the o^ory lobes. He ?hus recognize no cerebral hemispheres at all. and makes no fomparisou bfTween the sturgeon's brain and those of other fishes, nr the hisher Vertebrates. . It isTbe noted that this nomenclature of the two ^ntem^ pairs of lobes corresponds with that -WchGottsche had applied ?o the brains of osseous fishes, in 1835. This author 30, 445) enumerates the various names which had been given to the hinder and larger pair, and concludes that they are the olfactory lobes, the anterior paii being olfactory tubercles. Gottsche cites Des- moXs and'serres as regarding the so-called olfactory lobes as Cerebral lobes, which name has since been more commonly em- ployed Gottlche makes no definite allusion to the brains of other fishes than the Teleosts. . . ,,v,,i > - t - ,0 Based npon the pro.a.Ui^ that Z^^^^:'^^^^;:^^^^^^, ^ w^dZl from modifications by «f 7' «««^tV^^^!CThe morcompr;henslve group. rrr^idCiJ^ritrs^errnmbs. 4t *, '-^Ak> -^■: >^..'»H(ii,^.-A.-%,, '. "t "; xrnn i fm u t wm I) 170 B. NATURAL HI8TORT. In 1844 Johannes Miiller figured (18) the brain of Pohjpterua from above, from below, from the side and in single cross section, through the pair of lobes next to the anterior. There can be no better illustration of the slight importance as- cribed at that time to the brain for taxonomic purposes than the insufficient of figures and very brief des-'ptions, which the great ichthyologist devoted to the brain of a typical Ganoid. He says (p. 139) "Das Gehirn der Ganoiden ist eigenthumlich und unter- scheidet sich von dem der Knochenfische und Plagiostomen." Yet his description of the brain (p. 140) and r(imm& of the charac- ters (p. 141) give us only the optic chiasma, a feature which the Plagiostomes share with the Ganoids. (See also 41, 24.) Miiller enumerates the cerebellum and the optic lobes, the "lobus ventriculi tertii" (corresponding to the thalamus of higher vertebrates) the hemispheres, olfactory lobes and olfactory nerves. Although commenting upon the general resemblance of the brain to that of the sturgeon he does not call attention to the different determination which he makes of the two anterior pairs of lobes. In the following year Busch (29) published figures of several Ganoid brains. This work I have not been able to obtain. But if the figures of the brains of the sturgeon and the Chimera, copied by Owen (24, I, figs. 173 and 179), are fair examples, the work did not materi- ally advance the knowledge of either the form, the structure, or the homology of the ganoid brain. The paper of HoUard (34) admits three types of brains, the teleostean, the plagiostotne and the cydostome. It is not clear to which of these types he would refer the ganoid brain. In 1848, a pupil of Muller, H. Franque, figured (10) the brain of Amia from above and below with separate views of the optic chiasma. He makes no comparisons with other brains, and his description is a simple enumeration of the lobes according to the usual nomenclature, the two anterior pairs being olfactory lobes and hemispheres respectively. Dum^ril (4, pi. 20), copies from Phillippeaux and Vulpian figures of a sturgeon's brain from above and below. He makes no original observations. The so-called hemispheres are shown as solid rounded masses without eversion of the dorsal borders, and the olfactory lobes as solid without even the orifices distinctly por- trayed, though not interpreted, by Stannius and Busch. ■,-».«r,-f*' —rfi— .. — ■■•-tri ^'■•''^>i^ B. NATURAL HWTORT. 171 )rain of Polypterua ingle cross section, ght importance as- purposes than tlie IB, which the great Ganoid. He says mmlicb und unter- nd Plagiostomen." ium6 of the charac- feature which the JO 41, 24.) i optic lobes, the thalamus of higher d olfactory nerves. )lance of the brain on to the different 'ior pairs of lobes. figures of several ut if the figures of )ied by Owen (24, 'k did not materi- I, the structure, or pes of brains, the It is not clear to [)rain. red (10) the brain views of the optic 3r brains, and his I according to the ng olfactory lobes aux and Vulpian >w. He makes no ires are shown as }rsal borders, and ices distinctly por- Busch. In 1864, Mayer (40) published figures of a large ^^f^^\f fisies' brains, as illustrations of his idea that by the relaUve sue !nd mo e or less intimate connections of the brain-lobes, fish-hke jlrcTuld be divided into Pisces Mesencephali (Teleosts). and i;^^tfiSeo:r^.i:ri.»^^ Th:Cnt brain is represented by MiiUe^s figures ofMy.^ ani BdelLoma, and by an original and very ^oo^J^^^ofJe^T^^ ^yzm marinus. His interpretation of the parts differs from both ^ t^ngtelXrbrains are copies of G^eus ^r^^ Callorl.yr.^s^ from Busch, and of Torpedo from Savi ; the author addmg a fcata olusTzygcem, S^atim, Baia Scymnus and Chimera; all ^esro'wnfromab;ve,'c/»m«.a alone shows the olfactory lobes ; Te seplration of these fVom the rest of the brain in the figure is lot reCd" in the text or regarded by others who have copied ^hfbr'ain of Protopterus is seen from the side in a copy of nw«n's fiffure and ftom above in that of Peters. ° ZAX*. B»«h-, %u,e of the br.io of I^r^ ^L T' r ^Ja V.V it« Bide elves an original figure of that ot Jj. r«Tw^:ot llelVuPon the grfat difference andform and fl^rTs o^ the brains of Aci,enser Hurio and Buthenus, whUe hat TpXln agrees neither with them nor with the preparaUons lJ[eC^.. There are copies of Mailer's figure of the brajn of ^ZrZ^s and of Franque's of that of Amia. None of these SSicate the existence of a lateral ventricle or a foramen of ^The Ganoids together with the Dipnoans are called Hemiepen- oJhali The Holo-ganoidei Include Acipenser and Lepid<>steus, ^ht the HemUgancJdd embrace Araia, Polypterus, Protopterus "^^fs^mpatbizing with Mayer in his attempt to follow out the eJler suggestion of Cams, and make the brain the basis for a b'mLX fishes, I am compelled to eay that his detennmation '•**^^^'^%.;^ T*«., 'y ? ,„,^,„„ a Mmmm4tmmilifi^ 172 B. NATURAL BISTORT. Of homologiea and discrimination of groups, as founded upon the extfirnal aspect of preparations (some of which certainly are badly preserved) do not stand . the test of a careftil structural comparison. A smaller number of figures of sections or dissec- tions of a few typical fonns would have more materially aided our comprehension of the brains themselves and of the zoological relations of the flsh-like Vertebrates. In 1S68 appeared a paper upon the comparative anatomy and development of the brain by Miklucho-Maclay (41). «> Thisauthor regards the brain of Selachians as typical, and bases his determination of homologies upon the comparison of vertical longitudinal sections of the brains of an embryo shark (Heptan- chus) and a goat. He concludes that the cerebellum of the shark is a narrow bridge ; that the convoluted mass just in ftont, which is usually regarded as the cerebellum, represents the optic lobes; that the optic lobes are really the thalami (zwischenhim) ; and that the hemisiAeres (vorderhim) are only partly separated from each other. Remarking, in passing, that Miklucho-Maclay offers no sufHcient reason for the interpretation of the hinder lobes of the brain, I would call attention to the fact that the embryo shark was ISO""- (more than 5 inches) in length, and that, as shown by the figure, the so-called vorderhirn had already nearly filled up. His diagram of a typical brain (Fig. 1) is not readily or closely comparable with any fish-brain, as it seems to me ; and since the author adopts Muller's statement respecting the slight extent of the ventricles in the Myzonts; and neither describes nor flgurea any part of the brain of a Ganoid or Teleost, we are compelled to regard his interpretation of homologies throughout the branch as open to doubt, on account of the statement that the hemispheres of Ganoids and Teleosts are wholly separated (p. 560) ; this not being the case in any fish-brain excepting that of Protopterua, where the true hemispheres are separate as in Batrachians. Owen (24, 1, figs. 178 and 174) figures from above the brains of a sturgeon copied from Busch, and of Lepidosteus apparently original and very imperfect. In both, the masses just in front of the optic lobes are called prosencephala (hemispheres). But, as there figured, the outward aspect of the two brains is so dissimilar t.„r JAm"'''" "'"" H,"' "^^""^ '>y ""i «°t» »"ebrnary, 1876. The del»7 in pubUc*- tion of this paper eMbles me to UiBert a comment upon it. ■,«*s!*r-J a%t; if^'^'ieff^' B. HATUBAL HISTORT. 178 I founded upon the hich certainly are careftil etructural sections or dissec- laterially aided our of the zoological itive anatomy and (41). 90 I typical, and bases parison of vertical yo shark {Heptan- ellum of the shark ist in fi-ont, which ts the optic lobes ; ivischenhirn) ; and tly separated from oflTers no sufficient es of the brain, I • shark was 130""- own by the figure, 1 up. ; readily or closely le; and since the B slight extent of cribes nor figures ! are compelled to out the branch as ' the hemispheres p. 560) ; this not t of Protopterua, ktrachians. bove the brains of 'isteus apparently Bs just in front of pheres). But, as IS is so dissimilar The detoy in publics* of Monro" are represented in the stu^e ^^^^^^^ ti„ctly,but there is -^^f:^^^^T::Xl^:^..nr.^ bridge lum of the sturgeon is described as * «!"P' ^y its down- orfold-accordingtoit^^outw^^^^^^^^^^^ ward projection into the optic v««t"Cie cerebellum of the cerebellum has a very "^^f^f'^"^^^^^^^ «olid, whereas the gar-pike is figured as ^^^"^'"^ ^^^ ^^^^^^^, depressions. ,, U really Yroe^tnbTrTu) l^S^^^ flguL of fishes' The manual of Gegenoaur y ) aections of the brains brains. Three represent vertical longitudi^^^^ ^ of embryo shark, snake "'^'i g^'^^^^^^^;'^' ^Pg^s of the brain Although the first --^^^^^"^^^^^^^ brain of a shark of Polypterua are copied from Mullei, X^:^.y continent.. -^ '-• «f ^^'o "!" W. have no good English equivalent tor ^^^^^^ rr::rr^vr;^rt:L";::-I'.-^^^^^^^^^ not homogeneous; ;j" refrog and other aerial Vertebrates are that the hemispheres of the irog anu ^^^ optic lote, or m stark, "J "» "^^ °^ „, n, .^k .re died .."rl' fr^S WorS: .ocora.nee with the pi.n of the oX''f^""' ortroptio iobc, respective., 1.n.i,ph^^^ ' anatomlBtB. ■■1 ■;;;:jrmiSk~imBmMSS0' «%iHl mt>mmm fe!,. B. NATDBAL HISTORY. olfactory lobes. But he does not refer to the figure in the text nor does he mention the brain as liliely to aid either at present or in the future in the discrimination between the Ganoids and the other fishes. The figures and descriptions of the brains of Myzonts (Marsi- pobranchs), Teleosts, and Selachians (Elasmobranchs) are hardly more satisfactory. With none of them is any effort made to ascer- tain, by a structural comparison, the extent to which they conform to the type of brain commonly recognized among the air-breathing This is the more noteworthy because by far the clearest presen- tation of this type is f\imi8hed by the figures and descriptions in the earlier pages of the same work. For these diagrams indeed, as for so many others which bring orderly knowledge out of cha- otic detail, the anatomist is greatly indebted to Prof. Huxley. • In this brief historical survey, considering the general desire to ascertain the extent to which Ganoids form a natural group separa- ble from other fish-like forms, one is struck with the absence of both any attempt to characterize the group by means of the brain and of the supposition that such characterization is possible. Evidently the first step in such characterization should be the identification of parts, if possible, with those which uniformly exist in the brain of all air-breathing Vertebrates, the Batrachians, Reptiles, Birds and Mammalia. The ganoid brains upon which this paper is based, were all pre- pared by myself fVom fish just taken from the water. The differ- ence between these preparations and some previously made from specimens which had been transported for some distance or kept for a time in spirit before the heads were opened, has convinced me that, for the determination of doubtful j^oints of structure, the brain should be hardened in strong alcohol before the fish has been twenty-four hours out of water. The published figures and descriptions of ganoid brains with which I am acquainted appear to have been made from poorly preserved specimens. Moreover, none of them include all the views (from the side and from below as well as from above) and sections (mesio-longitudinal, and transverse at several points) which are necessary to the presentation of the rea't «t -jcture of a brain. With no other organ is it less safe to trubt to the external form find appearance of the several lobes. * igure in the text, itlier at present or Ganoids and the Mj'zonts (Marsi- anchs) are hardly 3rt made to ascer- liich they conform the air-breathing 5 clearest presen- d descriptions in diagrams indeed, ledge out of cha- rof. Huxley. • general desire to ral group separa- h the absence of ans of the brain is possible, n should be the which uniformly the Batrachians, ed, were all pre- ter. The differ- jusly made from listance or kept [, has convinced >f structure, the ihe fish has been Did brains with de from poorly include all the om above) and several points) : at: "icture of a to the external B. KATOKAt HMTOBT. 176 „„„ by a comparison ot f^ '^^'"^^^J^ „^, with th. «g- .ke m»i«l -'-"""alTo 0^r^24, 1, fig. 174), both ot Xb°'r'SKe':^° ftom poor,, pre^r,^* prep^-- tion8.«» ^. . ^^„ .-t__ tiie brain here represented, The gar-pike f-mwhvchwj« taken tt.e ^^^^^ .^ ^as a female, 1.3 "^^^'^^^i*?^^*,^^^^^^^^^^ so far as I know, with The brain, as is usual with this species , ^^„„ective tissue. all adult Ganoids, was covejed ^ J ^Aov^nmi jet black and This envelope is fatty and yellowi h m A^^^ ^^^ ^^^ ^^^^^^ ^^^ very alwndant in Po^oAm, ^^Tl^ light colored in A^o, and the cavity ; moderate in '^'°7^^' ^^^^^^^^^^ less than 120- long. iepfdo««e«s. In the young of t^««« \*^^^^^^^ .^rebral cavity. It iTenvelope exists, the brain <}« *« ^^^;^^^^^^^^^ commences the would be interesting to ascertain at what pe j::rrrr::nr:r-'r---'''°-''' Tbe ^,^^,,^tZ\-> ^ 20),«Ucb,wl.bun. brain, are those of Huxiey v**' & , - 34 r;;tant changes are. prod^^^^^^^^^^^ ,,^„, ^ th.ee According to Huxley s d««^"P J ^^ti^uous with the central ^ n^edian vesicles, w^^ose -vUi^ - ^^^.^^^ ..i.^ens below ^ canal of the spinal cord. The hm ^^^^ ^ ^^^ ^he become the medulla «W«nga^'*.;f >' ' the anterior part of this fourth veruncle (4) ^nd a bridge o^erJ^e^^ ^^^.^^^ ^^^^^^ ^^^ • ventricle is the '^''^^^""^ .^^^^j. J., of anthropotomy) ; its cavity » For Uie uee of w»eBe bbuhw. » ft IX-^x^ ««a W-*KWi 176 B. NATUBAI. HISTORT. This third ventricle is the cavity of the anterior vesicle, and its lateral walls become the thalami {Th). But from each side in fVont there is produced a hollow bud which enlarges so as to be- come the cerebral hemisphere (H). From the front of each hemis- phere a second bud is produced, the olfactory lobe {01). The cnvity of each hemisphere is a lateral (first or second) ventricle, (LV) and the cavity of the olfactory lobe is the olfactory ventricle. The constricted communication between each lateral ventricle and the median third ventricle is known as the ^^ foramen of Monro " (FM). Median dorsal and ventral outgrowths from the thalamus vesicle become respectively conarium ("pineal body," Co) and infundibulum, the connection of which with the hypophyAi (Hy) is now regarded as secondary (43, 92). The thin anterior wall of the anterior vesicle between the hemis- phere-buds, remains as the lamina terminalia (Lt) the "lamina cinerea" of anthropotomy. The corpus striatum is a thickening of the outer walls of the hemisphere {CS). The various trans- verse and longitudinal commissures corpus callosum, anterior com' missure, fornix and pons Varolii, probably do not exist in fishes and need not here be described. Taking for granted the sequence of principal ganglia, medulla, cerebellum, optic lobes, thalami, hemispheres and olfactory lobes, no difficulty is met in recognizing the three first named in the brain of Lepidosteua, But the appearance of these in the section differs considerably from the idea conveyed by the figures of the brain fi-om above and below. The fourth ventricle (IV) extends farther back, and has no bridge across its anterior end as in Huxley's figure. In this species the hinder end is quite sharply pointed. But in a smaller gar ft-om Wisconsin, not yet identified, the ventricle is shorter, its borders are raised and everted, and the hinder extremity less sharp. The borders also approach each other quite nearly, just behind the cerebellum, which, with a poorly preserved preparation, might lead an artist, not an anatomist, to regard them as normally continuous.^ If figure 7 be held with the olfactory lobe upward, then the sec- tion of the entire cerebellum may be compared to a letter S, the lower curve larger and its substance thicker than the upper. The lower, or, if the figure be replaced in the horizontal posi- x> Huxley's Sgan purports to be of the brain of L, temiratHatu$, Ag, QUnther re- garda thii as a synonym of L. o$$eu». • ,*- ^.. . -S* '*-lro B. NATUBAt HISTOBt. r vesicle, and its 'om each side in I'ges so as to be« it of each hemis- lobe (01). The second) ventricle, Ifactory ventricle. ral ventricle and xmen of Monro " om the thalamus )ody," Co) and lypophyUlB (Hy) wesn the hemis^ jt) the "lamina is a thickening 3 various trans- »i, anterior com' i exist in fishes inglia, medulla, olfactory lobes, ' named in the 3 in the section i figures of the e (IV) extends rior end as in B quite sharply ; yet identified, rerted, and the approach each , with a poorly I anatomist, to I, then the sec- a letter S, the 3 upper. >rizontaI post- >,Ag. GUntherrO' «on, posterior curve, '^P;:^ t^ ^W^T ^r.'"" anterior curve ^^^^^^P^^ .f^^jrof Gottsche" referred to by antbropotomy, and to the fornix ^^.^^ Huxley in his descnpt.on "fj^/ ^jf "^,^,^„e«3 of the cerebellum This part is about one-half J^e 'Wck ^^ Hself, an'd it becomes an -«-' "« \^J",^:;: lobes. The cere- the overhanging postenor bo dcr J^ *^ J ^elng more About midway '^f-Z^neST^ --^^^^^"^ portion upon cerebellum and the free thin edge or^ .^ .^ apposition the ventral aspect, Is a low ndge. ^^^^'^ J,„^^,. with a correspond ng ever ed edge o t^^ ^^ ^^^^ ^.,, , The dorsal surface of ^J« f ^f ^"J^,^ mounded portion f^om rather deep ftirrow separating the meai the peduncle on e«^^J» «;d;: .^g^ ^, ^ rather contracted passage The " aqueduct of Sylvius J^-^*^' . ,. ^ptic lobes. ftom the^ourth ventricle J^J^;— ^L^^^^^^ downward and The dorsal aspect of the optic ;3 ..^ ^i^e cerebellum m- forward at about the ^'^-^'^ 'fl^^tTlrfac. Is about the cimes back^rd. The t^^^^^^^/Jf °[ j^^ .?;„t the anterior margin same as that of the " fornix of Gottsche, but ^^^ ^ ts slightly thickened and rounded^ ^^^^^J^^acted aperture sur- °P*^°Tr^\^a^-2r'S^e cllmor pineal body (O lies rounded by a flarmg up- just In front of this aperture. doubting the correct- ^ So far there seems no reasonable cause fo^^^^ But the anterior half of the brain of ^»<^^««' ^^^^r^^, of the higher Verte- the way of strict comparison with the brates.3« ^^^ 2, 3, 4, cannot '•'•rrw B. (1«J . A. A. B. VOL. xxrr. a. f ■ '^ v 178 B. NATURAL HISTORT. tends under nearly the whole width of the brain and opens down- ward hy a median silt into what seems to be a plexus of vessels. The hollow lateral lobes are what Owen calls "hypoaria" and Huxley, with most authors, " lobi infcriores." The lower solid vas- cular mass corresponds to what is commonly called the pituitary body or hypophysis. It is easily detached, and is not, so far as I am aware, represented in any figure of a Ganoid brain. Pending an examination of the brain of Lophiua, the hypophy- sis of which lies far in front of the brain connected with its usual attachment by a very long inftindibulum, I am inclined to regard the lobi infcriores as lateral expansions"'' of what is called in anthropotomy the tuber cinereum. There remain to be described the two pair of m.i^ses which, in Lepidoateus as in most Teleosts, are placed jus* iii front of the optic lobes. They are at the present time usually regarded as representing respectively the hemispheres and olfactory lobes. According to the type of brain as described by Huxley and generally accepted, the hemispheres should be lateral masses separate from each other and each containing a cavity, the lateral ventricle, communicating with the median or third ventricle through a foramen of Monro. Yet, so far aa I am, avoare, no mci, condition of things haa been figured or described with respect to the brain of any fish-like form excepting Protopterua and Lepidosiren.^ (See Appendix.) In the brain of the adult Lepidoateua, the lateral mass marked PTh Is a solid lamina with its upper or dorsal border everted, as seen in the transverse section (Fig. 11). The mesial surface of its rounded dorsal aspect presents two fkirrows. It is Joined with its fellow of the opposite side by a large commissure (B)» and by a thinner lamina reaching back to the optic chlasma. " Dr. Cleland (88, 203) regards the hypoaria of osseoas dshet aa the thalami, and states that " in variuiis flgheH, the optic nerves arise from them as well as from the optio lobes." Dr. Cleland's learning and accuracy are such that I would not reject his view upon less grounds than those here presented. But I have not obterred the origin of the optic nerves from the hypoaria in any llsb. «• Tiedemann frankly admits (35, 864), that "we find no trace of lateral ventricles In the osseous Bshes;" he regarding the so-called hemispheres as ttie corpora striMta (p. «80). Contrast this with the loose statement of Vulpian (SI, 821), " on tronve parfols des rudiments de ventricules Interaux dans les lobes c^r^braux" of osseous fishes. The so-called ventricles of Selachians will be shown heraafter to be remnanU of th« third ventricle; not rudiments of the first and second. *• This is apparently what Oottsche called In osseous fishes, " commiiiura Interlob- nlarla." tJVS- ^*- •*• > ^. ■«wr»^«c -.-"^ •fc»»,-» • • I ■ tr-, B. NATURAL tllSTORT. 179 land opens down- |loxu8 of vessels. "bypoaria"and ! lower solid vas- |ed the pituitary I" not, so far as I ■brain. us, the hypophy. etl with its usual dined to regard hat is called in i.idseg which, in «« front of the »ny regarded as ictory lobes. by Huxley and lateral masses 'vity, the lateral k'entricle through ' things has been »y Jish-like form pendix.) al mass marked rder everted, as aesial surface of t is Joined with •e {B)« and by w »he thalami, and iIIasA-omttieoptio not reject hU view erred the origin of uteral ventrlclei in corpora ttriMta (p. on troure parfoia oaseoua flsiiea. • remnanu of th« imUaura intertob- Just in front of each of these lobes is a rounded orifice opening obliquely outward and forward into the base of the anterior or olfactory lobes. This orifice is wholly invisible from above or below or from the outer side, and, although figured by Stannius in the sturgeon, seems to have attracted no attention from those who have studied Ganoid brains. It leadfl into a cavity which extends the whole length of the so- called olfactory lobe, and is about 1"""- In diameter. As this is the only lateral opening from the median ventricle there seems to be no escape from the conclusion that it is the *' foramen of Mw* *■»»■» ■ • ^ J', ia> f*,->» 'v B. NATURAL niSTORT. 181 " 8Gcm to corres- ho third ventiiclo fPophysis below. |; which, however, of the material ■». thut it makes thalami or the |o is of no value jum is recognized he it is a bridge pmaller than the lie lobes in some other parts. e buds ft-om the '8, the offspring >e Ganoid brain, by their buds, as based upon nvoluted surface some way/uno- d be examined Jould be traced I'ith the ft-og by lented upon by in young spec- 'g the rudimen- •nro. No such t the sturgeon lings upon the ie fourth vent- apparently, of ina terminalis. development, ccome merely In a young Lepidosteus 151"""' long, the dorsal borders of tlie prothalnini re not everted as in the adult. For reasons wliich will be undorstood when the brains of Selachians and Myzonts are desoril>cd, I am inclined to think that at an earlier period of devel- opment the dorsal bonlers were united. Detailed descriptions of the brains of the other Ganoids are de- fcrrcd until figures can be presented. That of Aviia closely rc- BcmbluB that of LepidoHteua, especially in the cerebellum. The infundibulum is more folded. The crura thalumi are considerably longer. The brain of Acipenaer^° and Polyodon are very similar in both structure und general appearance. In both the cerebellum is apparently a narrow bridge, but, as seen in the figure of Stannius, it really extends far forward into the optic ventricle, as an exag- gerated fornix of Gottschc. The walls of the optic lobes are thicker In Polyodon than in Acipeneer, The brain of Scaphyrhyn- chua was not obtained for examination. There if no reason for supposing it to differ essentially from that of Acipenaer. MiJller's figures and descriptions of the brain of Polypterua do not allude to the communication between the median ventricle and the olfactory ventricles, but the figures are quite insuflScient, and pending its examination with reference to this point, we may infer that it agrees with Lepidoateua in this respect as in the eversion of the thalami. . . , The brain oft amoichthys is not known to me. We may even more naturally infer its agreement with that of Polypterua. Provisionally, at least, the seven genera, Amia and Lepidoateua^ Polypterus nnd Calamoichthya, Acipenaer , Scaphyrhynchua and Pol- yodon, maN l)e associated as having rudimentary hemiapherea in the form of nl'jhtly raised bordera of the foramina of Monro and much smaller than the olfactory lobea; large prothaXami connected below by a commiaaure but having their doraal bordera free and more or leaa everted; an optic chiasma; a rythmically contractile and multi- valvular bulbua arteriosus. Fig. 12 shows a mesial section of what seems to me to be a typical Ganoid brain with cross sections at characteristic points. Let us now see whether the above definition includes any other Vertebrates. »> Three species of this genus were examined, rubkundue, oxyrhynehu$, and t nndetermlnod. oneM yet undetermlnocl. -^.s^i^ mmMr T^.'i^i^l'** 182 B. NATURAL HISTOBT. Amphioxus appears to have only a medulla with a fourth ventri- cle. The part in ft'ont of the ventricle may be regarded as an un- differentiated representative of the brain of the higher Vertebrates (Langerhans (44, 297) says he finds a small olfactory lobe). In Myxine and Bdellostomd, Joh. Miiller (37), found no ventri- cle in front of the fourth, and no cerebellum. In a somewhat in- jured preparation of the brain of Myxine, I find what seems to be a thin and rudimentairy cerebellum ; and a median ventricle which extends forward to the base of the anterior pair of lobes, which Miiller and all other authors regard as the olfactory lobes. On each side at this point is a slit-like orifice leading into the cavity of the olfactory lobe. These can be no other than the foramina of Monro and lateral ventricles. The liemi spheres are hardly dis- tinguishable from the olfactory lobes. The larger pair of lobes just behind, since they form the walls of a median ventricle must be regarded as the undifferentiated prothalami and thalamr. They differ from thoib of Ganoids in being connected above as well as below. But behind them are the conarium and the orifice of the optic ventricle just as in the brain of Lepidosteus. In Petromyzon Miiller found (87) the third ventricle only. In several well pre- served preparations of the brain of the large sea-lamprey (P. marinus, var. Americanus), I find at the anterior extremity of this median cavity, as in Myxine, a foramen of Monro leading intO' the olfactory or lateral ventricle. The thalami are closed above as in Myxine. The distinct lobes which project just behind the olfac- tory lobes are probably hemispheres. (See Appendix.) Miiller describes the optic nerves of the Myzonts as not crossing at all. Upon this ground, aa by the non-separation of the thalami above and the lack of several rows of valves in the bulbus arte- riosus, they differ from the Ganoids. In figure 13 {M) i» repre- sented a cross section of the brain of Petromyzon through the thalami. (See Appendix.) The Selachians (here restricting the term to the sharks and skates) have a brain which is really only a complex modification of the Lamprey's. In an embryo shark {Mustelus eanis) 37""°- (about IJ inches) i« length, that part which gives rise to the olfactory crura and which has been variously interpreted as hemis- pheres alone, hemispheres and thalami, and thickened lamina ter- minalis, is a large vesicle with thin walls and a single cavity. This communicates behind with the optic ventricle and om each aMif.««»»^4 ")r^ ith a fourth ventri- regarded as an un- higher Vertebrates ractory lobe). [)» found no ventri- In a somewhat in- what seems to be an ventricle which tir of lobes, which factory lobes. On ng into the cavity than the foramina >res are hardly dis- kger pair of "lobes 'ian ventricle must fl thalami. They above as well as the orifice of the 3' In Petromyzon J several well pre- p sea-lamprey (p. r extremity of this ro leading into, the 5losed above as in behind the olfac- endix.) its as not crossing an of the thalami the bulbus arte- 13 {M) is repre- «o» through the the sharks and lex njodification lu8 eanis) 37'»"n- ves rise to the ►reted as hemis- aed lamina ter- single cavity, e and on each B. NATURAL HISTORY. 183 side in firont with the cavity of a little bud which is in contact with the nasal sack. The vesicle is evidently the expanded prothalamus closed above as in the Myzonts. In the adult Selachians (as I hope to show by a series of figures at a future time) we must suppose the original median cavity to have gradually filled up so as to leave only two slender passages, near the lower wall, which start fVom opposite the optic foramen behind, and diverge to enter the olfactory ventricles in front. The degree of differentiation of the crura thalami, and the hemispheres, will be more fully described hereafter. In some forms the hemispheres are distinctly con- stricted from the sides of the nearly solid prothalamus. Although, therefore, the optic chiasma and multivalvular and contractile bul- bus and some other characters are common to Ganoids and Sela- chians, the prothalamus is open in the former and closed in the latter. In these and some other respects the contrast between the two groups is noteworthy. In figure 13, ES represents a cross section of the prothalamus of an embryo shark and AS that of an adult. The Holocephali (Chimera and Callorhynchus) are commonly arranged with or near the Selachians. They have many features in common and the intromittent organs upon the ventral fins are usually regarded as very important. Being a purely sexual appa- ratus we may question whether their taxonomic value is equal to that of the brain. Not having had the opportunity of examining a brain 31 I can only judge from the figure by Busch, copied by »Ju8t as this goes to press I am enalJIed, through the kindness of Mr. Alex. Agassis, to expose and examine the brain of a well-preserved male Chimera in the Museum of Comparative Zoology. The oerebellnm is very large and covers the optic lobes; but is not folded transversely as in most, if not aU, adult sharks and skates. The crura thalami are very long and thin and united ventrally by a delicate membrane apparently only pia mater. Anteriorly each cms expands Into a prothalamus, the dorsal border of which is thin and slightly everted. This prothalamus, however, instead of forming the principal anterior mass as in Qsnoids, Is overlapped outside by a large and elon- gated hemisphere abouPS°"»' in height and 16'»- in length. On the hinder third of the mesial surface is a large rounded foramen of Monro, 4f^ in diameter. The lateral ventricle extends forward into the olfiictory lobe. Into the fttramen, and occupying its entire area, projects a thickening of the outer wall of the hemisphere which may rep- resent a primordial corpus striatum. Just in ftt>nt of the foramen the ventral borders of the hemispheres are connected by a transverse oommissuro. I greatly regret not having been able to examine this brain before presenting this paper. It seems to flir- nish an actnal form intermediate between the apparenUy distinct types represented by the brains of Selachians, Ganoids and Dipnoans. If I correctly interpret the appear- ance of a partial subdivision of the elongated mass behind the olfactory lobe the Chi- mera's brain presents a more equal proportion of hemisphere and prothalamus than exists in Ganoids or Teleosts, where the former seems to be reduced to a rudiment hardly recognizable as such. -^^^ ^nf^ mi . II ( W '^-'sw^ I f •fAAsurjj \-»f^..~. I. 184 B. NATURAL HISTORY. Owen (24, fig. 179). The cerebellum appears like that of the sharks and skates. But the elongated crura thalami, and what seem to be somewhat expanded prothalami, and the rudimentary hemispheres, indicate a close similarity with the Ganoid type. The brain should be carefully reexamined, and that of a very young embryo would be especially valuable. The figure of the brain of Protopterus (Owen, 25 and 24) might be taken for that of Menopoma or Menobrmchus. It has no appar- ent resemblance to either the Ganoid or the Selachian type. There are also true nostrils, and, according to Huxley (7, 147), a small pulmonary auricle. These characters united with those of the brain seem to offer strong grounds against the association of the Dipnoi with the Ganoids, excepting as a very generalized type combining Ganoid and Batrachian features. 'The brain of Cera- todua has not been described.^* Of fish-like forms there remain the Teleostei. They may at once be distinguished from all others by the non-rythmically con- tractile bulbus provided with a single row of valves and by the decussation of the optic nerves without a chiasma.^s A sufficient number of Teleost brains has not yet been care- fully examined to enable us to generalize with safety. But so far' as they are known we may characterize them as having solid lateral masses (prothalami), their dorsal borders separate and sometimes everted, and with the olfactory lobes sometimes in contact with the prothalami, sometimes in contact with the olfactory sacks and connected with the prothalami by more or less elongated crura. Since this paper was presented t have found small foramina of Monro and ventricles in Perm flavescens, Anguilla Bostoni- ensis and Scomber vemalia. They, however, are much smaller "In "Natare" for Jan. 6th, 1876, It i. .tated that Prof. Hnxley described, for the flrst time, the brain of Ceratodut at the meeting of Uie Zoological Society, Jan. 4th : that he showed how closely It resembled that of Lepidoiiren, and that in some points it resembled th« Selachian rather than the Ganoid type. He laid especial stress upon the affinities of the animal with CAfmera. Zoaioglsts win look with great interest for this paper on acoonnt of the descriptloa and flgiires of the brain of a form which has aroused so much discnssion, and also for the morphological and tazonomic considerations which can hardly faU to throw irreat light upon the relations of the flsh-like Vei tebrates. " Gottsche (30, 476, aad flg. xxxiii), refers to a remarkable rariation of the optio nerves described by Weber (Meckel's Archly. 1873, p. 317). In an example of Clupea ftar«Hj«. t)-, ncrre of the left eye was pierced by that of the right. The ttructure of the chiasma of Ganoids and Selachians should be oareitally examined to ascertain how completely the libers cross, or intermingle, or connect the eyes and lobes of the two Bides together. .7 v-s-^-- . ry sacks and ted crura. •all foramina nlla BoatonU luch smaller iscribed, for tba iy. Jan. «h; that some points it stresB upon tlie the descriptioB •n, and also for ' So tbrow great » of the optio »Ple of Clupta "o structure of ••nertain liow e« of tlie two B. NATURAL BISTORT. 185 than in Ganoids, and I give a provisional figure (Fig. 14) mainly for the purpose of calling attention to the point where they are to be looked for. Probably they are proportionally larger in embryo brains. They may become wholly obliterated in some adults, es- pecially those with olfactory crura. They should be looked for in large species, as Esox^ Xiphias, Hippogloama, etc., where the olfactory lobes are sessile.^^ The following table exhibits the above mentioned charaet^s in a more condensed form. But it must not be inferred that the order of names indicates my belief respecting either their rank, their aflQnities, or geological succession. In the first place no linear arrangement can do this. In the second, while the Teleosts seem to most perfectly and abundantly embody the Jish idea and their geological relations and the structure of some parts would lead us to place them highest in the fish series, yet the non-ming- ling of the optic nerves and the very embryonic condition of the kidneys as compared with those of Selachians,^^ seem to place them next the Myzonts. The air-breathing Vertebrates are added in order to complete the series. Provisional Arranoehent of Vertebrates according to Cere- bral AMD Cardiac Characters. Leptocardii. (Amphioxus). Brain not differentiated from medulla. Heart a contractile tube. Mtzonts. (Maroipobranchii). Optic nerves do not cross (Miiller). Single median nostril. Hemispheres smaller than ol- factory lobes. Thalamus and prothalamus not distinctly sepa- rated. Thalamus closed forward and dorsad. Cerebellum a narrow and thin lamina; perhaps wanting in Myrinolds. (See Appendix.) Selachians. (Elasmobranchii.) Optic chiasma. Rhythmically contractile bulbus arteriosus, with several rows of valves. Olfac- tory lobes ' pedunculated. Hemispheres smaller than olfactory lobes. Prothalami and thalaml distinct ; the latter as crura. In ** The brains mast be well preserved. M As reoenUr studied by Balfour (38, 80). ,j».»«*:ft*<"!««WH3iSSK^ -* i» *iiIR3re??*'^^^t. -, ;.:*:*«a(»aetiti aer-.t IM B. KATURAL BISTORT. embryo the prothalamus a thin-walled vescicle, with a sinele ^vity which, in adult, is reduced to two canals diverging forward. Prothalamus remains closed forward and dorsad. Nostrils in pairs, but do not enter mouth. Cerebellum folded transversely. HoLOCKPHALi. Brain combines characters of Selachians, Ga- noids and Batrachians. Crura thalami much elongated. True hemispheres, larger than prothalami or olfactory lobes. Foramen of Monro very large. (The last two sentences have been added since this paper was read. See notes 31 and 36.) Ganoids. Optic ohiasma. Rhythmically contractile bulbus arteriosus with several rows of valves. Hemispheres rudimentary. Olfactory lobes sessile. Prothalami separate forward and dorsad, and more or less everted. Cerebellum with no transverse folds, foramina of Monro large. Teleosts. Optic nerves cross but form no chiasma. Bulbus arteriosus not rhythmically contractile and has a single series of valves. Olfactory lobes sessile or pedunculated. So-called hemis- pheres are probably prothalami; more or less everted as in Ganoids, and separate forward and dorsad. True hemispheres rudimentary or absent. Foramina of Monro and lateral ventricles small or, perhaps in some, obliterated. (Last sentence added since this paper was read.) DiPNOANS. Hemispheres larger than olfactory lobes. Heart tnlocular. True nostrils. Optic chiasma. (Should probably be ^ranged with or near Batrachians in the Series of air-breathing ^ Batrachians. Hemispheres larger than olfactory lobes. Heart tnlocular. Optic chiasma. No corpora striata or commissures. Walls of brain thin and ventricles large. True nostrils. Reptiles. True hemispheres. True nostrils. Corpora striata and anterior commissure. Heart tnlocular or quadrilocalar. Right and left aortic arches persistent* Birds. Same brain characters as in Reptiles. Heart quadri- ".t^3«a^_^■--- >*^ » •>* < T^ . ^ - . <-• 1 pith a single |rging forward. Nostrils in ransversely. Blachians, Ga- ^gated. True Bs. Foramen N been added actile bulbus rudimentary. I and dorsad, isverse folds. ma. Bulbus gle series of sailed hemis> erted as in hemispheres •al ventricles tence added hes. Beart probably be r-breathing •es. Heart mmissuref. }ra striata w. Bight B. NATURAL BISTORT. 187 t qaadri. looalar. Right aortic arch persistent. (Birds seem to be an aberrant group of Sauropsida.) Mammals. Corpora striata. Anterior commissure. Corpus callosum. Fornix. Pons varolii. Heart quadrilocular. Left aortic arch persistent. By characters of the brain alone the Ganoids are readily sepa- rable from all other vertebrates. From the Teleosts they differ in respect to the optic chiasma ; also, so f ' as now known, on ac- count of the greater size of the lateral vwntricles and foramina of Monro.^ But differences of size alone are not reliable ; and our knowledge of the structure of the Tcleost brain must be much ex- tended before final generalizations can be made. Meantime it is interesting to note that some cerebral characters seem to associate the Ganoids with the Teleosts, while others, with cardiac charac- ters, link them with the Selachians. The Teleosts are apparently dn aberrant group, like the Birds. Minor modifications of the brain, together with those of the tail and air-bladder, will probably furnish the basis for subdivision of the Ganoids. The brains of Amia and Lepidoateua are very nearly alike, and both seem to agree in all essential respects with that of Polypterua, and, by inference, CalamoicJithya. The brains of the Sturgeons resemble one another more closely than they do those of the other genera, but all agree in the rudimentary hemi- spbece, the enlarged prothalami, and the position of the foramen of Monro. Reserving for the present any discussion as to the separation c' Dipnoans from Batrachians, and of Birds from the other Sanrop sida, the groups seem to readily fall into five categories. The first and lowest includes Amphioxua elone. The second the Myzonts and Selachians, whose brains are differentiated, but bave not. yet assumed the distinctive features of either the true aquatic or the aerial Vertebrates. They have the form and habit of fishes, but their brains are more readily comparable with those of Batrar chiaus. For the hemispheres are distinct, though small, and the thalamus remains closed, instead of being separated forward and >• At Uie time thU paper was preMnted I had not been able to And these openings In any Teleostean brain, and therefare supposed that their existence in the Ganoids ftkimed a sharp distinction between the two groups. .\'ffort could tructurally nade some mistakes as to both fact and interpretation, for the sake of the advantages which I am confident will attend the careful and systematic reconsideration of our present methods of classification. These last are almost purely empirical. They have, as in the case of the Ganoids, led to the most diametrically opposite conclusions. Would it not be worth while to enquire whether, from both analogy and experience, cerebral and cardiac characters are not more trust- worthy for the discrimination of larger groups, and whether char- acters drawn from the skeleton, teeth, digestive and reproductive systems are not likely to serve us better if restricted to the deter- mination of orders, families and genera. When the limits of classes and sub-classes have been once as- certained by the study of the heart and the brain, most of the fossil forms may, by the correlations of their hard parts be assigned to places in them. At present, on account of the greater availability of hard parts for preparation and preservation, we practically depend upon them almost entirely, or tacitly assume that they are of greater taxonomic value than the soft parts, and that the latter are, therefore, readily correlated with the former. SuHHART. 1. The smallest Lepidosteus here described (18°™- long), has a primordial median fln extending over the hinder third of the body above, and its hinder half below, interrupted at the vent. 2. The locations of the dorsal, the anal and the infra-caudal fins are marked by coloration and thickening of the primordial fin. 8. A fourth or supra-caudal fin is also indicated, though less decidedly. This fin is not functionally developed. 4. The tail of this smallest Lepidosteus is nearly protocercal, the end of the body inclining ulightly downward. 5. The end of the body proper is gradually forced upward by an increase of the infra-caudal lobe, and becomes the " filament " already known in the young gar-pike. 6. The movements of this filament are extensive, and vibratory, and wholly voluntary. 7. The filament exists, though evidently in process of removal, in a young Lepidosteus osseus 300""- long. 8. The iniVa-caudal lobe becomes the functional tail of the adult. 9. The vertebral column is then continued obliquely upward and backward as a tapering cartilaginous rod which terminates at a point corresponding with the previous separation of the filament ii-i3&i.ri---JiBfc:- 0^ U-s- 190 B. HATDBAL HIBTORT. ft-om the infVa-caudal lobe. This point coincides with the hinder- most of the dorsal fulcra. 10. This rod comprises the notoohord, the spinal cord and two lateral cartilaginous pieces. 1?. The tail of the adult Amia presents a similar structure, excepting that the rod is shorter and there are no fUlora. 12. It seems probable that the tail of Amia passes through stages like those of Lepidoateua, but the smallest specimen here described (70""^ long) shows no sign of the filament. 13. The two earlier stages of the tail of Lepidosteus may be compared with the protocercal (or diphycercal) and the ordinary heterocercal tails of other living and fossil forms. The maaked heterocercal tail of Amia and Lepidoateua probably existed in Megalurua and some other mesozoic forms, but is not known among the palffiozoic fishes. It likewise exists in the embryo of certain Teleosts, as Oaateroateua and the Siluroids. 14. The pectoral fins of Lepidoateua attain considerable size before the appearance of the ventrals. 15. The latter are not lobed, but the former consist of a fleshy lobe and a thin fVinge or border. 16. In the smallest Lepidoateua the branchiostegal membranes are separate farther forward than in the adult. The point of their Junction in the young becomes a transverse fold, which may cor- respond with the hinder border of the jugular plate of Amia. 17. The "foramina of Monro" and lateral ventricles have been found by me in the following Ganoids : — Amia, Lepidoateua, Aci- penaer and Polyodon; and in the following Teleosts: — Perca, Scomber, AnguUla; in Chimera;^ in the following Selachians: — Muatelua, Carchariaa; and in the Myzont genera Myxine and Petromyzon. There is good reason to believe that Scaphyrhyn- chua, Polypterua and Calamoichthya have the same parts ; and that they exist in other Teleosts, but less easily seen than in Ganoids, or perhaps wholly obliterated in the adults of some species. In both Ganoids and Teleosts the fdramen of Monro seems to open into the base of the anterior or olfactory lobe on each side. 18. Aside, therefore, fi-om the difiierence in general aspect and in size of the foramina and ventricles, the Ganoid and Teleost brains, as heretofore, are most readily distinguished by the cAuumia which exists in the former group. "As ttated on nrevloas page* the foramina wer* found In CMmtra and tha T*- leotU aRor thU paper waa preaented. ""' ' "iltililff ' F ■ ' " ' nn ■m il i i'iiiiiii I .\i-" the hinder* tord and two |ar structure, Bra. 8808 through ecimen here fleua may be Ithe ordinary I The nuuked existed in Known among yo of certain derable size It of a fleshy |I membranes )oint of their lich may cor- ' Amia. '8 have been iosteus, Aci. ts: — Perca, lachians:— . Vyxine and Scaphyrhyn- 3 ; and that in Ganoids, pecies. In as to open ide. aspect and id Teleost B. NATURAL UIBTORT. 19. We may regard, provisionally, the seven genera, Amia, Lepi- dosteua, Polypterua, Calamoich''.^., Acipenser, Scaphyrhynchua and Polyodon (together with such fossil forms as are obviously allied to them) as constituting a natural group (class or sub-class) charac- terized by an optic chiaama; a rhythmically contractile bulbua arteri' oaua with aeveral rouia of valvea; large prothalami aeparate above byit united below; rudimentary hemispheres; and the foramina of Monro opening apparently into the base of the sessile olfactory lobea. 20. It seems probable that by features of the brain and heart alone, all of the primary subdivisions of Vertebrates may be accu- rately characterized. 21. The Dipnoans, hitherto regarded as fishes and usually arranged with or near the Ganoids, agree with the Batrachians in cerebral and cardiac and other characters. This group seems to furnish a case for testing the relative tazonomic value of charac- ters derived f^om the brain and heart on the one hand and ftom the skeleton, limbs and digestive organs on the other. In like manner the brain of Holocephali would indicate that they belon nearer the Ganoids than the Selachians, perhaps as a transition between the two. 21. While the facts and considerations presented in this paper cause me to doubt the correctness of all classifications of fish-like Vertebrates hitherto proposed, they do not seem to Justify the framing of another system. Nor is it probable that any phyllo- genetic arrangement can be proposed which shall either advance science or reflect credit upon the propounder, until our knowledge of the embryology, of the brains and of fossil forms is much more extensive than at present.^ Appendix. — Just as this goes to press I have been able to oon« suit the admirable paper of Paul Langerhans, *'Untersuchungen nber Petromyzon Planeri," pp. 114, 16mo, 10 Tafeln. Freiburg, 1873. This author figures and describes (p. 83) the lateral and olfactory ventricles of Petromyzon. He also states (p. 95) that an optic chiasma does exist. These statements must be considered in connection with paragraphs upon pages 178,182, 185 of this paper. 1 As this paper li psMing throngb the pr«M, I bare seen in the ■■ Zoological Beeord" for 1873. page 86, an abstract of a memoir by Panoeri and De Sanctis " Sopra alounl organl delta C^halopttni, Napoli," 1860, 4to. The authors recognise font types of brain besides that in AmpkU>xu$ i namely, in Cydostomata ; in Teleosts ; in fonr Selachian gear •ra, JHetrobatU, Xygana, MtUobatU, n-ygon i and in all other Selachians and Ganoids. No mention is made of the lateral venfc'iclea or foramina of Monro, and, so Ar aa- in.) 16. LtlTKEN, C. : On the limits and classification of the Uauoidt. (Translation.) (Annals and magazine of natural history, May, 1871. 320-330.) 17. Cope, E. D. : Observations on the systematic relations of flshet. (Proceedings Am. asso. for adv. of science, 1871, 317-343.) [Preliminary publication, slightly different, in American naturaltsi, 1871, 579-506.] 18. MOller, Johannes: Ueber den Baa nnd die Grenzen der Ganolden und Uber das natilrliche System der Fische. ( Abhandling der KttnigUchen Akademie der Wistent- chanen zu Berlin, 1844. 4to, 117-216,) 16 plates. 19. GOhther, Albert: Description of Ceratodut, a genus of Ganoid flshea re- cently discovered In the rivers of Queensland: Australia, (Pbllosphical transaotlont, 1871,511-571. 42 plates.) 20. AOASSIZ, Louis : A journey In Brazil, 8to., pp. 540. Illustrated. 1868. 81. AOASBiz, L. : An essay on clarsiflcation. 6vo, pp. 381, London, 1850. 22. AoASSiz, Louis : The clatslfication of the Silurold flshet. (Proc. Boston too. nat. hist., Dec. 18, 1868. p. 864.) 23. W YUAN, Jeffries : Anat'omyof the aervous system of Aana ptfrfm*. (Smith- sonian contributions to knowledge, v, ait. 4, 1855, quarto, pp. 51. 2 plates. 84. Owen, Richard: Comparative anatomy and physiology of vertebrates, 3 volumes, 8vo, pp. 2155. 1471 flgures. London, 1861-1868. 85. Owen, R.: Description of Zepidcriren ( Protopterui) anntetem. (LInnaan transactions, xviil, 827-381)., 5 plates. 86. Newberry, J. 8.: Description of fossU flshet of Ohio. pp. 110, 17 plates, (Geological survey of Ohio. Vol. 1, 1878.) — ^-'SS* gpMteiM MMMnuC ■e*^'.- ni- 00. lOl. ho- les, the I ted aU. islal 1870. the Hut- LOlrt nlan and urea. itean lion.) lings ireQt, Uber inns- en TO- tloni, \ BOO. Jmith- ites, 3 innan plates. "§ NATURAL HISTORT. 193 IT. PoiT, r. : Observations on lUfforont points In the natural hiatorx of Cuba. (Annals of the lyreum of nnt. hist. N. Y., 1858. vt, ISO.) S7, WiLDP.R, B. U. : The lateral position of the vent In AmphU>xui and In certain batrachinn larra). (Proc. Am. asso. for adT. of science, 1873.) pp. 'i.\ 10 llgureii 38. MULi.Kn, J. : nerlcht Uber die KorUtihrltto dor verglelchenden Aoatomie der WIrbelthloro In Jahro, 1841. (Arohir nir Annt. 18«i; coxxxvlll-cdxl.) M. Buscil, W. : Oe Selnchloruin et ganoldeorum eniiephulo. 4to; 1818. 80. aoTTROHB, C. M.: Vorgl. Anat. des Ouhlms der Oratonflscho. (Arrh.fUr Anat, ISM; m-^H, 488-486; Taf. Iv und vl.) 31. VuLi-iAN, A.: Lofons sur la physlologie g4n, the pectoral fln conilating of a rounded fleahy lobe £ and a thin lyinge /*; 1 , 9, 8, 4, S, regions of the primordial median fln. V, the vent. C, the commencement Of the InfVa-oaudal lobe. The commencing anal la seen between T, audi'. Z>, the com* nenctng dorsal fln; X, indicates a slight and transitory modiflcalion of the primordial fln like a aecond doraal, or, more probably, aupra-caudai lobe. The ventrals have not appeared. The lines above flgurei 1, 1, 8 Indicate the actual length of the young Ltpi- Tig. 9. Tall of young ttptdciteui 29"- In length, enlarged 4 diameters. The letter* ingaslnflg.l. Theinfr.. 3audal(C) begins to project beyond the outline of the primor* dial fln. V« the ventral fln. Fig. 3. Tnllofyottng£fpMo«<«iui44'W'in length, enlargodldiameters. Letteringaa in flg. 9. The primordial fln exists pnly upon the borders of the filamentary tormina* Uon of the body {ti) which Is now crowded up by the increasing inftra-oaudal lobe. Fig. 4. Tail of young LepidoiteH* niitui WOf*- long, natural site. The Infl-a-oaudal lobe now occupies Its permanent place as the flinctlonal tall, while the fllament ( Fi) bat nearly disappeared. Its base is protected by six pair of fUlcra {DF) and a similar Mrlet covert tLo anterior half of the lower border of the tall ( VF). Fig. 8. Dissected tall uf medium sized £«p. platyitomut. The fllament has disap* peared and the (Ulora extend backward to a point nearly corresponding with Its sepa- ration from the caudal flu. 'To this point may be traced a cartilaginous rod (H), the prolongation of the vertebral column ( VC), and previously continued into the fllament. This rod consists of the notochord, the spinal cord (5(7), and a cartilaginous sheath. NC, neural canal laid open. HC, hamal canal, laid open. Fig. 6. Section of the upper margin of the tall of L. platyitomui at a point about mid-way between the base of the fln and the last pair of fUIcra; enlarged. Jf, noto* ehord; SC, spinal cord; CS, cartilaginous sheath, in which the vertebra are afterward developed. F", points of the upper nilora; F*, cut surfaces of the next lower fUlcra; F, cut surfaces of the lowest ftalora which are separated so as to embrace the upper half of the cartilage. CJt', cut surface of the uppermost caudal fln ray, the two halves being separated above to enclose the lower part of the cartilage. The dark line ijrossing the section Indicates the commencing splitting of the ray Into two. CR, the halves of the second fln ray not quite perfectly apposed, and Joined by a double mem- brane to the rays above and below. ••AU the flgnret were drawn, ttom tpeciineni and preparatlont, by Mr. Philip Barnard. (194) >4 -|^-> ^k '"' ' ■ ^wwmw»» W I I.DKU. l-'iu;> I. ViMiiiK Li'l'lil'i"!''!!'. I'lilitrw'') ■< illiiiiiuli !''< KIk- i' Tail or yoiiiiK l.<>|>li|i>nluiH, oiiIiii'k<'r young LeiiUloHtoiis, naliintl hIzd *,f4 ., .-^v*- •.■ -V ..t'-^'»' in length ; 1, Lepidotteui osaeus; 3, young Lepidotttut, 800»«' in length; 6, Polyodoni 7 and 8, ^M^ ' ^ ' * y