Section of Zoology and Botany. 491 



ZOOLOGY AND BOTANY. 



On the Principles of Classification in the Animal Kingdom in ge- 

 neral, and among the Mammalia in particular. By Professor 

 Agassiz. 



Although the principal groups of animals are impressed with 

 such characters as to be easily recognised and to admit of little 

 doubt, yet their order and succession have been determined by no 

 general principle. This appears from the discrepancy in the posi- 

 tion assigned to them by the most eminent systematists, each of 

 whom has assumed arbitrarily some organ or system of organs for 

 the basis of his arrangement. Professor Agassiz, after adverting to 

 some German naturalists who alone have sought after a general 

 principle which should be satisfactory to " philosophic natural- 

 ists," passed in review the classes of the animal kingdom, each 

 of which, he stated, exhibited in an eminent degree the develop- 

 ment of some one of the animal functions. While Vertebrate ani- 

 mals (with Man their type) arrive at the greatest perfection in 

 the organs of the Senses, the Invertebrate offer in the class of 

 Worms the representative of the system of Nutrition, in Crustacea 

 of Circulation, in Insects of Respiration, and in Mollusca of Genera- 

 tion. The Professor next proceeded to demonstrate in what man- 

 ner each subclass of vertebrate animals derives its peculiar charac- 

 ter from some one element of the animal ceconomy. 



This predominant element is the bony skeleton in Fishes, the mus- 

 cular structure in Reptiles, the sensibility of the nervous system in 

 Birds, and the perfection of the senses in Mammalia, which there- 

 fore reproduced the distinguishing character and constitute the type 

 of vertebrate animals. He next showed that each of the other sub- 

 classes of the higher group is represented among the Mammalia 

 along with its own peculiar type. He explained his reason for the 

 fourfold division which he had adopted in the subclass, pointing out 

 the close affinity which connects the Ruminantia, the Pachyder- 

 mia, the Rodentia, the Edentata, and the herbivorous Marsupialia, 

 (in none of which is the true canine tooth developed,) which he con- 

 siders as forming a single group ; in another he unites those cha- 

 racterized by the presence of the canine tooth in its proper function 

 (as an instrument of nutrition, not merely of defence), viz. the 

 Carnivora and those Marsupialia which partake of their character, 

 and the Quadrumana. The Cetacea form a group in themselves ; 

 and Man another. The manner in which these represent the sub- 

 classes of Vertebrata was exhibited by the comparison of 



Cetacea, with Fishes, 



Ruminantia, &c. Reptiles, 

 Carnivora, &c. Birds ; 



while Man is the perfection and type of the mammiferous confor- 

 mation. 



Prof. Agassiz thdn applied this principle to illustrate the order 

 and succession of the groups in Mammalia by a reference to the or- 



3R2 



