258 



The Study of Animal Life part hi 



pools are scarce, the young, after living and breathing for a time 

 within the mother, are born as lung-breathers ; also in some 

 species of tree-frogs {HyloJes), which live in situations where water 

 is scarce, the gilled stage is omitted. 



The development of the common frog should be studied by 

 every student of natural history. The eggs are fertilised as they 

 are being laid. The division of the ovum can be readily observed. 

 In its early stages the tadpole is fish-like, with a lamprey-like 



Fig. 53. -The life-historj- of the Frog. 



mouth. External gills are replaced by an internal set, and as 

 metamorphosis is accomplished these disappear and the lungs 

 become active. The larva feeds first on its own yolk, then on 

 freshwater plants, then on small animals or even on its own 

 relatives ; then it fasts, absorbing its tail, and finally it becomes an 

 insect-catching frog. 



The food of adult Amphibians usuall)' consists of insects, slugs, 

 and worms ; most of the larvje are for a time vegetarian. Though 

 Amphibians often live alone, crowds are often found together at the 

 breeding season. Then the sluggish life wakes up, as the croak- 

 ings of frogs remind us. Quaint are many of their reproductive 

 habits, to some of which allusion has already been made. Such 



