14 THE INFANCY OF ANIMALS 



smaller D. dorsigera) have lost their pouches, and carry 

 their young, after the method invented by the koala, on 

 their backs. 



But while the koala has but one young one to cater for 

 at a time, these American species have each to accommo- 

 date a litter. Happily they have developed long pre- 

 hensile tails ; and the young swiftly acquire ability to 

 put theirs to very good purpose, twining them round the 

 mother's tail, which for this purpose is arched over the 

 back ; thus anchored, and with a firm grip of her fur, 

 they can travel everywhere. But when we recall the fact 

 that both the koala and these opossums are tree-dwellers, 

 it gives one furiously to think why the koala should be 

 tailless and the opossums should have developed taUs 

 of such an exceptional character. Further, it seems 

 hopeless to ask, Why, among these opossums, should some 

 have retained the pouch while others have lost it ? 



So far as the evidence goes the conditions of existence 

 are alike in all. May we assume that the loss is due to an 

 " inherent " tendency to suppress the pouch, a tendency 

 which might have proved fatal to the well-being of the 

 species, which would have vanished without leaving a 

 trace of the cause of disappearance, but happily the or- 

 ganism responded by changing the fashion of nursing ? 



In many respects the history of young bats is even 

 more remarkable than that of the young marsupials, 

 inasmuch as they are borne about by their mothers on their 

 aerial journeys in quest of daily bread. If all accounts 

 be true, some of these living flying machines carry not 

 only more than one passenger, but contrive to do this even 

 when the burden exceeds the weight of their own bodies. 



Thus Mr. Hudson, in his entertaining volume " The 

 NaturaUst in La Plata," tells us that " while taking bats 



