FUNDAMENTAL RELATIONS OF ANIMALS 47 



studied them with particular care, "the Marsupialia present a re- 

 markable diversity of structure, containing herbivorous, carnivorous, 

 and insectivorous species; indeed, we find amongst the marsupial 

 animals analogous representations of most of the other orders of 

 Mammalia. The Qiiadrumana are represented by the Phelangers, 

 the Carnivora by the Dasyuri, the Insectivora by the small Phasco- 

 gales, the Ruminantia by the Kangaroos, and the Edentata by the 

 Monotremes. The Cheiroptera are not represented by any known 

 marsupial animals, and the Rodents are represented by a single 

 species only; the hiatus is filled up, however, in both cases, by pla- 

 cental species, for Bats and Rodents are tolerably numerous in 

 Australia, and, if we except the Dog, which it is probable has been 

 introduced by man, these are the only placental Mammalia found 

 in that continent." Nevertheless, all these animals have in common 

 some most striking anatomical characters which distinguish them 

 from all other Mammalia and stamp them as one of the most natural 

 groups of that class; their mode of reproduction and the connection 

 of the young with the mother are different; so also is the structure of 

 their brain, etc.^^ 



Now the suggestion that such peculiarities could be produced by 

 physical agents is forever set aside by the fact that neither the birds 

 nor the reptiles, nor, indeed, any other animals of New Holland 

 depart in such a manner from the ordinary character of their repre- 

 sentatives in other parts of the world; unless it could be shown that 

 such agents have the power of discrimination and may produce, un- 

 der the same conditions, beings which agree and others which do not 

 agree with those of different continents; not to speak again of the 

 simultaneous occurence in that same continent of other heteroge- 

 nous types of Mammalia, Bats and Rodents, which occur there as well 

 as everywhere else in other continents. ^^ Nor is New Holland the 

 only part of the world which nourishes animals highly diversified 

 among themselves and yet presenting common characters strikingly 

 different from those of the other members of their type, circum- 

 scribed within definite geographical areas. Almost every part of the 

 globe exhibits some such group either of animals or of plants, and 



**See Owen, "Marsupialia," in R. B. Todd, Cyclopedia of Anatomy and Physiology 

 (4 vols., 1835-1852), and several elaborate papers by himself and others, quoted there. 



^ [In Chapter IV of the Origin of Species Darwin cited Waterhouse's findings as 

 evidence of divergence of character fostered by natural selection.] 



