CHAPTER TWELFTH. 



METAMORPHOSES OF ANIMALS. 



366. UNDER the name of metamorphoses are included 

 those changes which the body of an animal undergoes after 

 its birth, and which are modifications, in various degrees, of 

 its organization, form, and its mode of life. Such changes 

 are not peculiar to certain classes, as has been so long sup- 

 posed, but are common to all animals, without exception. 



367. Vegetables also undergo metamorphoses, but with 

 this essential difference, that in vegetables the process con- 

 sists in an addition of new parts to the old ones. A succession 

 of leaves, differing from those which preceded them, comes 

 on each season ; new branches and roots are added to the 

 old stem, and woody layers to the trunk. In animals, the 

 whole body is transformed, in such a manner that all the 

 existing parts contribute to the formation of the modified 

 body. The chrysalis becomes a butterfly ; the frog, after 

 having been herbivorous during its tadpole state, becomes 

 carnivorous, and its stomach is adapted to this new mode of 

 life ; at the same time, instead of breathing by gills, it be- 

 comes an air-breathing animal ; its tail and the gills disap- 

 pear ; lungs and legs are being developed, and, finally, it is 

 to live and move on land. 



368. The nature, the duration, and importance of meta- 

 morphoses, as also the epoch at which they take place, are 

 infinitely varied. The most striking changes which naturally 

 present themselves to the mind when we speak of metamor- 



