MODIFICATION OF REPRODUCTIVE PROCESS 71 



presence there causes, in some mysterious fashion, the 

 skin to grow up into a ledge all round, forming a kind 

 of saucer-shaped receptacle in which the eggs are borne 

 about (Fig. 40). In another South- American Frog 

 Nototrema (Fig. 41) the same thing happens, but in 

 this case the rim of the saucer grows more actively on 

 each side and turns inwards, so that eventually the two 

 edges meet and form a roof over the eggs, which thus 

 come to be contained in a deep pouch, opening by a 

 narrow slit which may be further reduced to a small 

 pore at its hind end. 



Then there is the extraordinary Surinam Toad Pipa. 

 In this case also the eggs are deposited on the back of the 

 female, spaced out at intervals, and their presence causes 

 the skin in their neighbourhood to grow up round the 

 eggs so that each one comes to be enclosed in a deep pit 

 or cell which is closed in by a closely-fitting lid. Each 

 in its narrow cell, the young toads proceed with their 

 development, passing through the Tadpole stage before 

 eventually they emerge to lead their independent existence 

 (Fig. 42). 



Lastly may be mentioned the little South-American 

 toad, Rhinoderma darwini, in which the male parent 

 swallows the eggs into the croaking-sac or sounding 

 chamber which lies under the skin of the breast, and in 

 the safe seclusion of which the young toads proceed 

 with their development. 



It will probably be admitted by everyone that the 

 cases of these Frogs and Toads constitute an extra- 

 ordinarily interesting series of attempts to get rid of the 

 free aquatic existence during the early stages of the life- 

 history. 



It is only, however, when we come to the Reptiles and 



