THE "GENERAL MORPHOLOGY" 221 



water. The young ones develop from these eggs, 

 and find themselves in the water. The most 

 practical adaptation for them is to swim about by 

 means of a tail and breathe by means of gills like the 

 fish. They do not reach land until later, and they 

 creep on to it and have an equipment of the oppo- 

 site character, with legs and lungs. 



But this explanation throws no light on the 

 question why the frog lays its eggs in the water. 

 However, there might be some utility or other, 

 some need for protection, for instance, in that. 

 Let us take a few other cases. 



There are several species of tree-frogs, and toads, 

 and closely related amphibia like the salamanders, 

 that do not lay their eggs in the water. Some 

 of them bury them in folds of their own external 

 skin, others (such as the Alpine salamander) retain 

 them within the mother's body, as the mammals do. 

 The young animals develop there from the eggs. 

 Even there, however, where there is no question 

 of aquatic life, the young frogs, toads, and sala- 

 manders first assume the fish-form. The young 

 frogs and toads have fin-like tails, and all of them 

 have gills. There seems to be some internal law 

 of development that forces the frog and its relatives 

 to pass through the fish-stage in their individual 

 evolution even when there is no trace whatever 

 of any external utility. 



Now let us examine the matter as Darwinians 

 and believers in evolution. 



There are reasons on every hand for believing 

 that the frogs and salamanders, which now stand 



