THE FROG AS PARENT. 



75 



father, carries the young with her. In the Brazilian tree-frog (Hyla 

 Goeldii), it is again the mother who bears the young with her. The 

 eggs are very large and whitish and crowded together into a rounded 

 mass on the back of the female, as represented in Fig. 9. While all the 

 other frogs as yet mentioned seem to have no special organ or apparatus 

 for holding the eggs or tadpoles as they carry them about with them, 

 this Brazilian frog is provided with a growth of skin on its back to 

 form a wall all around the eggs so that they lie in a spoon-like depres- 

 sion. The knowledge of such a change in the skin of the back for egg- 

 carrying may make us more ready to receive the accounts of the Sur- 

 rinam toad described by Mile. Merrain in 1705. When, in 1725, the 

 Dutchman Euysch described the remarkable pits for carrying yoimg 

 which this creature has upon its back, the account met with nat- 

 ural skepticism, but at the present day reiterated observations place 



Fig. 9. 



t'lo. 10. 



the main facts beyond doubt. The female of this toad (Pipa dor- 

 sigera), as seen in Fig. 10, bears its young upon its back, each in a sep- 

 arate case, like so many papooses. 



The cases are made at the breeding season, and before that the two 

 sexes look alike. How the eggs get into these special receptacles is still 

 an unanswered question, though the male may be a factor in the case; 

 at all events, when the male goes away after being some twenty-four 

 hours on the back of the female, the spawn is found on the back of 

 the female, where the eggs gradually sink down into circular pits, that 

 are hollowed out in the skin, and are 10-15 mm. deep. When an egg 

 has sunk down into one of these pits, a thick, leathery or homy roof 

 forms over it, and thus shuts it out from the external world. 



These roofs are 5-6 mm. thick, and have a dark color unlike the 

 rest of the back. Whether they, like the rest of the chamber about the 

 egg, are formed from the skin, or whether they may be modified rem- 



