THE DARWINIAN THEORY 



Fig. 15. 



B 



Stages in the development of the common Frog (Rana temporaria). 



A.— The egg. x 3 



B. — The Tadpole at the time of hatching. The mouth is not yet 

 formed, the Tadpole being still dependent on the food-yolk present in 

 its body. Two pairs of external gills are present as branched finger- 

 like processes at the sides of the neck. Below and in front of these 

 is the horse-shoe shaped sucker by which the Tadpole fixes itself, and 

 at the sides of the front of the head the rudiments of the nose and eye 

 are seen. x 3 



C. — A Tadpole shortly after the time of appearance of the limbs : the 

 hind limbs are seen at the junction of the body and tail : the fore limbs are 

 present, but are concealed by the opercular folds covering the gills. At 

 this stage the Tadpole breathes by both gills and lungs. x 1 



D. — A young Frog with the tail only partially absorbed. x 1 



