REPRODUCTION 187 



Eggs deposited simply in the water and larvae which 

 pass through a lengthy metamorphosis in that element are 

 naturally exposed to many dangers, hence the enormous 

 number, often amounting to thousands, produced by one 

 female annually. On the other hand, many contrivances 

 have been resorted to by which the young are protected during 

 their frail, early stages, in which case Nature has practised 

 economy in the number of eggs, which varies in direct pro- 

 portion to the chances of destruction. 



These contrivances fall under two heads, which may be 

 found combined in some forms : firstly, protection by the par- 

 ents, either by means of nests or nurseries, or by direct nursing ; 

 secondly, shortening of the metamorphosis, which is hurried 

 through within the egg, the young leaping out into the world 

 in the perfect condition in which ordinary frogs leave the 

 water. The different modes of protection will be made clear 

 by the following synoptic arrangement : — 



(1) Protection by means of nests or nurseries. 



A. In enclosures in the water. 



B. In holes near the water. 



C. In nests, on trees or rocks, overhanging the water. 



D. In a transparent gelatinous bag in the water. 



E. On trees or in moss away from the water. 



(2) Direct nursing by the parents. 



A. Tadpoles transported from one place to the other 



by the male. 



B. Eggs protected by the male, who covers them with 



his body. 



C. Eggs carried by the parent. 



a. Round the legs by the male. 



b. On the back of the female. 



a. Exposed. 



/3. In cell-like pouches. 



7. In a common pouch. 



c. On the belly, exposed, by the female. 



d. In the mouth, or in a gular pouch. 



a. By the male. 

 /3. By the female. 



D. Eggs retained in the uterus (viviparous species). 



