92 METAMOKPHOSES OF MAN 



Tliey have not faded away, they have not simply 

 fallen off, they have not been cast off by a species of 

 moulting, as in the case of insect larvae. They have 

 been got rid by none of these methods ; their sub- 

 stance has been re-absorbed, atom by atom; and 

 hence, although it has ceased to exist, it is not the less 

 alive on that account. 



We see then that frogs undergo complete meta- 

 morphoses, not only in regard to their entire organism, 

 but as to each set of apparatus, with the exception 

 of the nervous system. The salamanders are not 

 similarly situated. These maintain their external 

 gills throughout the entire larval period, and never 

 acquire internal branchiae. When reaching the air- 

 breathing condition, they skip, as it were, one of 

 the transformations which frogs undergo. The sala- 

 manders have also four legs in the perfect state; 

 but then, in addition to these, they preserve the tail. 



The metamorphoses become simpler and simpler as 

 we approach the lower grades of this peculiar class. 

 The Proteus, which is found only in the subterranean 

 lakes of Carniola, and the Axolotl, which inhabits the 

 lakes in the interior of Mexico, retain the gills all 

 through life, and as they possess lungs also, they can 

 breathe by air or water indifferently, — they are really 

 amphibious animals. Finally the Lepidosiren, that 

 type of transitional beings, presents even in the adult 

 state, and in regard to its circulatory and other 

 apparatus, such a combination of the essential cha- 

 racters of reptiles and fishes, that the most skilled of 

 living anatomists are divided as to its true position, 

 and are unable to say to which of the two classes this 

 really paradoxical creature belongs. 



