MODIFICATION OF REPRODUCTIVE PROCESS 69 



Budget! and Agar studied in South America, the spawn 

 is deposited between the leaves of plants overhanging the 

 edges of pools. Here it hangs while the eggs undergo 

 the early stages of their development, but when the Tad- 

 pole stage is reached a kind of digestive juice is secreted 

 which causes the jelly round the eggs to soften and 

 liquefy and trickle down into the pool, carrying the 



FIG. 38. 

 Alytes obstetricans, male carrying eggs. (After Boulenger.) 



tadpoles with it. Here then the tadpole has to pass the 

 later part of its existence in the water, but all the earlier 

 stages are independent of the water. 



A somewhat similar case is that of a Japanese Tree- 

 frog (Rhacophorus schlegeli), where the mass of spawn is 

 deposited in a burrow excavated in a bank of earth, by 

 the margin of standing water. After depositing their 

 spawn the parents make their way out by a tunnel sloping 

 downwards towards the water's surface, and when the 

 appropriate stage of development has been -reached the 

 jelly becomes liquefied and trickles, with its contained 

 tadpoles, down this tunnel into the water. 



