ii4 COMPARATIVE ANATOMY vin 



climbing, were preserved and accumulated on the Darwinian 

 hypothesis, the hallux (a common part in all mammals, only 

 in abeyance when not wanted) was redeveloped in a form best 

 adapted for its actual purposes, the other digits gradually 

 resuming their normal condition ; these two, however, still 

 preserving strong reminiscences of the ancestral state. 1 



It is certainly significant that all the Australian vegetable- 

 feeding climbing opossums have feet constructed on this type, 

 one that is similar to that of the kangaroos of the same 

 country, while the American opossums, further removed 

 geographically, and therefore, in all probability, in actual 

 relationship, with feet functionally the same, show no trace 

 of this deep-seated structural peculiarity a peculiarity most 

 important for the consideration of the philosophical anatomist, 

 as it evidently depends on some more far-reaching cause than 

 mere adaptation to purpose. 



In considering a little more fully the application of such 

 views to the study of morphology, I must say a few words on 

 classification. It was felt at the very outset of the study of 

 natural history that without some system of classification the 

 subject was little more than a hopeless chaotic confusion. 

 The first instinct of a zoologist is to arrange in some sort of 

 order the multitudinous objects with which he has to deal. 

 In the beginning of science, with little sound knowledge, such 

 classifications were often mere arbitrary arrangements, founded 

 on some easily accessible peculiarities, and forming nothing 



1 In New Guinea and North Australia there are actually species of kangaroos, 

 constituting the genus Dendrolagus, which habitually reside in trees ; not climb- 

 ing among the smaller boughs, as is the manner of the koalas and opossums, but 

 sitting on the larger horizontal branches. Their feet present a marked deviation 

 from those of the common kangaroos of the plains, the deviation being in the 

 direction of the feet of the koala. They are shorter and broader ; the lateral 

 toes are relatively more developed, and are on the same plane with the fourth or 

 large toe, and although they have no hallux or first toe, the bone of the tarsus 

 (internal cuneiform), which usually supports that digit, is of relatively larger size. 



The phalangers, a family of climbing vegetable-feeding marsupials, form another 

 link in the structure of their feet between the kangaroo and the koala, though 

 most nearly resembling the latter. On the other hand, in a very remarkable 

 little ground - dwelling animal, the Chwropus, the kangaroo type of foot is 

 modified in the opposite direction, all the digits except the fourth being reduced 

 to excessively rudimentary proportions. 



