68 AFFINITIES AND HABITS OF THYLACOLEO, 



animal which had become exclusively carnivorous perfect the 

 same type of dentition for an exclusively carnivorous diet. 



The second question arises out of Flower's proposition already 

 quoted. In considering it there is one important fact that must 

 not be overlooked, namely, that while among large herbivorous 

 animals many parts of the organisation become so highly specialised 

 to suit the vegetable diet that it would be impossible for the 

 animal to alter its diet very materially and thrive, in small 

 animals the specialisation is much less marked, and a considerable 

 variety of diet is possible. Thus, while it would be impossible 

 for an ox or a kangaroo to become a carnivorous animal, many 

 of the smaller Rodents and some of the small Phalangers which 

 are normally herbivorous occasionally take to eating flesh, and a 

 number of the small Phalangers are partly insectivorous The 

 Bandicoots afford a well known instance of a group of animals which 

 are partly herbivorous and partly insectivorous; and among the 

 Insectivora other instances occur. JMacroscelides, the Elephant- 

 shrew, has a jaw which judging by analogy would certainly be 

 referred to a herbivorous form and the molar teeth would seem 

 to be quite in harmony with this determination, and yet though 

 JIdcroscelides is largely a vegetable feeder I have found in the 

 stomach abundant remains of ants and even of fairly large 

 beetles. But perhaps in no Order is there a more remarkable 

 instance of change of diet than in the Chiroptera. Had Pferopus 

 been first discovered as a fossil it would, according to the reason- 

 ing of Falconer and Flower, almost certainly have Ijeen regarded 

 as an insectivorous or carnivorous form. Here we have a form, 

 it would be held, closely allied to the insectivorous bats and 

 having a very similar type of dentition— large canines separated 

 by a row of small incisors — almost exactly as in the normal 

 carnivorous types and quite unlike that found in the normal 

 vegetable feeders, and the conclusion would be arrived at that 

 Pteropus was either an insectivore or a carnivore, but most pro- 

 bably not a vegetable feeder. And yet the conclusion would be 

 wrong. But were Cuvier's jarinciple taken as the guide only a 

 correct conclusion could be arrived at. 



