64 INTRODUCTION. 



semblage ;" but I think we might, on the other hand, 

 say, with safety, that all the most eminent anatomists 

 (these being at the same time zoologists) agree in 

 uniting them at least all who have written on the 

 subject, and who have had the necessary materials 

 for forming a just opinion. I could wish, however, 

 that this important question should not rest upon 

 authority ; but to go through the train of reasoning, 

 by which the anatomists have arrived at their con- 

 clusions, would require more space than can be 

 spared in a volume like the present one, and, more- 

 over, would not be suited to a popular work. 



It has often been stated that the Marsupiata 

 consist of animals of most dissimilar organization, 

 and are united together only by a single peculiarity . 

 whatever little weight some zoologists may attach to 

 this single peculiarity, its value was almost immedi- 

 ately appreciated by the anatomists and physiolo- 

 gists. But I will now proceed to show that the 

 animals under consideration are united by many 

 peculiarities these serving to distinguish them from 

 all other quadrupeds, whilst the rich collections now 

 in the British Museum, and in that of the Zoological 

 Society, show that the most dissimilar forms of 

 Marsupial animals are closely linked together by 

 species exhibiting the intermediate grades of structure. 



The most striking peculiarity in the Marsupial 

 animals consists in the premature birth of their young, 

 and consequently the imperfect state of development 

 which they present at this period compared with 

 otiier Mammalia. The young of the great Kangaroo, 



