THE ARGUMENT FROM EMBRYOLOGY 101 



Fig. 16. 



A B 



D 



Stages in the development of the West Indian Frog (Hylodes) : illus- 

 trating the effect of increased amount of food-yolk in causing the omission 

 of ancestral stages. The free living Tadpole stage of the common Frog is 

 entirely suppressed, and no gills are ever formed. The entire development 

 from the laying of the eggs to the hatching of the Frogs occupies from a 

 fortnight to three weeks, 



A. — The larva at the end of the first week. The head, eyes, stumps of 

 the limbs, and the long tail are well shown. The food-yolk is contained 

 within the large yolk-sac in the middle of the figure. x 3 



B.— The young Hylodes shortly before hatching. There is still a very large 

 tail present, which is believed to be used as a respiratory organ. x 3 



C. — Young Hylodes at the moment of emerging from the egg : a short 

 stump of a tail is still present. x 3 



D. — Young Hylodes at the end of the first day. The tail is completely 

 absorbed, and the Frog has already the form of an adult. x 3 



