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Show 94 ON CLASSIFICATION. tros mihi occurrerc vid ntur pia -ntro typi, qnor1nn pnmn14 I. ··b secundus £ ris tertius simiis et h01nini proprius st." gIll us, : . . . In this passage lVIannnals arc clearly divided, In tho first place, into placental and i~placental; and th forn1 r arc then subdivided into those wluch hav a non- ad neon. and those which have a eaducous uterine pla nta. rl1ho Cetacea and u naulate Mammals constitute th fonncr group ; tho Uodonts, b Carnivores, Apes, and M n tho ]att r. In 1843, an accmnpli hcd E no·1i h zool gi. t, l\Ir. \Vaterhonse, publi h d a highly in tructiv paper on tho "Classjfi. cation of the Mammalia,"* in which tho following passage occurs:- "Taking tho general form of th Brain into consideration, the placental l\iammalia woul a1 p n,r eli vi iblc into two sections: first, tho e in whi ·h t.h c rcbn nn i g nerally of a round d form, obtu e in front and I r vid l with distinct convolutions; and se ondly, th .·e in whi h the c r bnnn is c~estitnto of convolutions, or ne<trly so, and u ually contracted in front. Tho fir t divi ion w nlcl (' nt ain th Quacl1·umana, Carnivora, Cetacea, P cwhyde?'ntata, and R'Ll?ninantia, and tbe second would contain the Chei1·optm·a, I nsectivo?-ct, Edentata, and Rodentia." But although l\Ir. ''at rh use puts forwanl tlm clearly the facts upon which a c r bral c1a, ~i:fi ·ation of the Mammalia might be based, he inunccliat •1y aft rwar ls with his customary judgment, xpre e:3 gr at c1 n t a t th value of any such clas ification. "nut are we in a c nclition t tak for a ba. i of classification of the llfa1nmalia the stru tnr of tl1 Lrain? I think not, though, in the ea f th llfa1·s~~pialia, it hns afforded characters serving to , parat that fr01n oth r sections, and to indicate it. prop r po ition in the y. t m. I am not prepared to follow tho naturali t. who would, in th pr s nt state of information, take thi organ a.· on f pri1nary importa11ce in the distribution of th ord r of ih plac •nt aJ · ric of l\Iammals. I cannot adopt the tw gr at , etion f this series as apparently * "Annals and Maga zin of a iural Ili~:dory ,'' 184H, vol. xii. P· 390. WATER.HOUSE AND MILNE-EDWARDS. 95 indicated by the smooth anrl. anteriorly contracted ~rel rum on the one hand, and the convolnted cerebrum, with It r undecl anterior portion, on the other. Wore I to do so, I should ~nd it necessary to ren1ove some of the Lemurs from their group .In the highest order of the first section, and to place them 1n the second section." In the succeeding year, 1844, M. lVIiln -Ed ward ·, one of th , most distinguished physiologists and zbologi. ts of modern France, proposed, in a highly philosophical paper. :1~011 zooleaical classification in general,* a method of ubdivlding tho Mammalia, essentially si1nilar to that put forward incidentally by Von Baer and Eschricht, but lacking, as I conceive, what is the great merit of the latter writers, namely, the clear perception of the classificatory value of the intimate structur of the placenta and the entrance, or not, of a de idual nt rine ele1nent into its composition. M. Milne-Ed ward dw -.l]s with great force (as Mr. Waterhouse had previou 1 y clone) upon the closeness of the general structural affinities which unit th Rodentia, Inseativora, Cheiroptera, Quadrumana, and B imana of Cuvier together, and shows that these affinitio are denoted by the discoid placenta which they po se s in common. The diffused placenta (under which head the cotyledonary placenta is included) is stated to be the characteristic of tLe Ruminantia, Pachydermata, Edentata, and Cetacea; whil , lastly, the " Carnivora and seals (Amphibies) are distinguished fr01n all the rest by their zonular plaeenta." The singular genus Hyrax, which Cuvier end avour d t prove to be a true Pa hyderm, is con icl red by l\1. l\IilneEdwards to form one of the series of l\Ta1mnal with a zonular placenta; and to represent, in that serio , the Pachydenn in th series with diffuse placentation, and the Rodents, in the cnes with discoidal placentation. M. Gervais, in Franr-o, and M. Vogt, in Gernu1.ny, have adopted the placental classification of Milne-Ed wards ; while, in 1857, Mr. Waterhouse's proposed, but immediately rejected, cerebral classification was substantially revived by Pl'ofessor * "Annales des Sciences naiurclles." Serio 3. Tome 1. "Con idcraiion sur quelques Principcs roln,tifs it ln Classification Jl n. turcllo des Animn.ux." |