in.] INDEPENDENT SIMILARITIES OF STRUCTURE. 81 



Mammals 8 are divisible into one great group, which 

 comprises the immense majority of kinds termed, from 

 their mode of reproduction, placenta! Mammals, and into 

 another very much smaller group comprising the pouched- 

 beasts or marsupials (which are the kangaroos, bandicoots, 

 phalangers, etc., of Australia), and the true opossums of 

 America, called implacental Mammals. Now, the placen- 

 tal mammals are subdivided into various orders, among 

 which are the flesh-eaters (Carnivora, i. e., cats, dogs, ot- 

 ters, weasels, etc.), and the insect-eaters (Insectivora, i. e., 

 moles, hedgehogs, shrew-mice, etc.). The marsupial mam- 

 mals also present a variety of forms (some of which are 

 carnivorous beasts, while others are insectivorous), so 

 marked that it has been even proposed to divide them into 

 orders parallel to the orders of ^lacental beasts. 



The resemblance, indeed, is so striking as, on Darwinian 

 principles, to suggest the probability of genetic affinity ; 

 and it even led Prof. Huxley, in his Hunterian Lectures, in 

 1866, to promulgate the notion that a vast and widely-dif- 

 fused marsupial fauna may have existed anteriorly to the 



TEETH OP TTBOTBICHU8 AND PERAJ4ELE8 



development of the ordinary placenta!, non-pouched beasts, 

 and that the carnivorous, insectivorous, and herbivorous 



3 I. e., warm-blooded animals which suckle their young, such as apes, 

 bats, hoofed beasts, lions, dogs, bears, weasels, rats, squirrels, armadillos, 

 sloths, whales, porpoises, kangaroos, opossums, etc. 



