OEDER OP MARSUPIALS. 17 



seizing them with her lips. This is how she proceeds in this opera- 

 tion : applying her two fore-paws with force to the sides of the pouch, 

 she drags these sides in opposite directions, so as to distend thera 

 and enlarge the opening, as we do when we untie a small bag or 

 purse. She then introduces her muzzle into the pouch, and lying 

 on the ground, so as to be in the most favourable position, she 

 extracts the foetus, which has passed through the first phase of its 

 existence. Then, without its ever using its members, she places it 

 over one of her manxmse, which it would be powerless of itself to 

 reach, and holds it there till it has seized the teat. Arrived at 

 this point, the young one has no further need of its mother's 

 assistance ; it adheres firmly to the teat, and cannot be separated 

 from it unless some external violence is used. Nevertheless, its 

 strength is not yet sufficient to render it capable of self-sustenta- 

 tion ; that is to say, it is as yet incapable of sucking in the milk 

 by which it is to be nourished. To prevent this from causing the 

 young one to waste away and die of starvation, the female is pro- 

 vided with a muscle, which, by contracting on the teat, causes the 

 milk to be injected into its mouth. From what is stated above, 

 we see that the essential difference between the Marsupials and the 

 other Mammalia consists in their young requiring a mammary 

 nourishment at a much less advanced period of their development. 

 The marsupial bones, and the purse supported by these bones, are 

 the consequences of this necessity. 



During the second period of gestation, the organization is com- 

 pleted ; the new creatvire approaches more and more to its perfect 

 form and final state of development. In the larger Kangaroos, the 

 hair appears in the sixth month. From the beginning of the eighth 

 month, the young Kangaroo puts its nose frequently out of doors, 

 that is to say, protrudes its head from the marsupial purse, and &s 

 a prelude to its approaching independent existence, nibbles here 

 and there the tender grass. At last it makes its entrance into the 

 world, and ventures a few timid jumps, as it follows its mother. It 

 begins now to live on its own responsibility ; but for some time it 

 will return to its former hiding-place, either to find there a place 

 of refuge in case of danger, or by its mother's mdk to make up 

 for the insufficiency of the nourishment which its weak state has 

 allowed it to procure. So one may see sucking at the same time great 

 young ones almost emancipated, and weak creatures the produce of 



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