XVm PROCEEDINaS OF THE 



Society to discontinue, fi-om the present time, the publication of 

 their quarto Transactions, will in all probability restore to us a 

 portion of our lost prestige : and I cannot qiut this subject with- 

 out pointing with particular pleasure to the paper by Professor 

 Owen, lately read at our Meetings, which I unhesitatingly pro- 

 nounce to be one of the most complete and profoundly philoso- 

 phical examples of zoological generalization it has for a long time 

 been my lot to listen to. The importance and interest attaching 

 to this essay made me anxious to present you with an abstract of 

 its reasoning, but my time will only allow me to give a very hasty 

 sketch of the principal positions taken by the author. 



With respect to the first part of the paper on the characters of the 

 Mammalia, its vakie chiefly consists in the additions to those usually 

 given in zoological works, and they evince the same laborious and 

 long-continued research as characterizes aU Professor Owen's pro- 

 ductions. His own views are based upon the constancy of certain 

 modifications of the brain in certain proportions in the class 

 Mammalia, and on the importance of those cerebral characters. 

 The first of these, discovered by the author many years since in 

 the brain of the kangaroo, and since ascertained by him to be 

 common to the Mai'supialia and Monotremata, is the absence of 

 the supra-ventricidar part of the corpus callosum, and the reduction 

 of the commissural part of the hemispheres to the anterior com- 

 missure and fornix. With this is associated the non-development 

 of the placenta, the premature birth of the ofi'spring, the presence 

 of marsupial bones and other characters. To this primary divdsion 

 or subclass, the lowest in its organization, the author gives the 

 name Lyencephctla. The second stage in the cerebral development 

 consists in the presence of the corpus callosum, but connecting 

 hemispheres as little advanced in bulk and external character as in 

 the former. The animals thus characterized are termed Lissence- 

 pjiala, which include the orders Hodentia, Insectivora, Cheiroptera, 

 and Bruta. In the third subclass, the Gyrencepliala, the cerebrum 

 extends over more or less of the cerebellum and olfactory lobes, 

 and the superficies is ordinarily convoluted ; and in this subclass 

 are placed the orders Cetacea, Sirenia, Toxodontia, Proboscidea, 

 Perissodactyla, Artiodactyla, Carnivora, and Quadrumana. But 

 the most important application of the cerebral characters is that 

 by which man is raised, by the present classification, above the 

 rest of the mammalia, not merely as a distinct order, but as the 

 type of a subclass. " Not only," says the author, " do the cerebral 

 hemispheres overlap the olfactory lobes and cerebellum, but they 



