METAMOnPIIOSES OF A.tlMALS. 183 



tration. The young White-fish, as we have seen, (315,) is 

 fur from having acquired its complete development when 

 born. The vertical fins are not yet separate ; the mouth has 

 not yet its proper position ; the yolk has not yet retreated 

 within the cavity of the body, but hangs below the chest in 

 the form of a large bag. Much, therefore, remains to be 

 changed before its development is complete. But the fact 

 tliat it has been born does not prevent its future evolution, 

 whicK goes on without interruption. 



389. Similar inferences may be drawn from the develop- 

 ment of the chicken. The only difference is, that the young 

 chicken is born in a more mature state, the most important 

 transformations having taken place during the embryonic 

 period, while those to be undergone after birth are less con- 

 siderable, though they complete the process begun in the 

 embryo. Thus we see it, shortly after birth, completely 

 changing its covering, and clothed with feathers instead of 

 down ; still later its crest appears, and its spurs begin to be 

 developed. 



390. In certain Mammals, known under the name of 

 Marsupials, (the Opossum and Kangaroo,) the link between 

 the transformations which take place before birth, and those 

 that occur at a later period, is especially remarkable. These 

 animals are brought into the world so weak and undeveloped 

 that they have to undergo a second gestation, in a pouch with 

 which the mother is furnished, and in which the young remain, 

 each one fixed to a teat, until they are entirely developed. 

 Even those animals which are born nearest to the complete 

 slate, undergo, nevertheless, embryonic transformations. 

 lUmiinanls acquire their horns; and the lion his mane. Mosi 

 mammals, at birth, are destitute of teeth, and incapable of 

 using their limbs; and all are dependent on the mother and 

 the milk secreted by her, until the stomach is capable of 

 digesting other aliments. 



