AMPHIBIANS 



439 



means of protection is obviously necessary, and this is found in 

 the presence of one or a pair of modified sticky areas on the under 

 side of the head, by means of which the larva adheres for some 

 time to a water-plant. 



We now pass to the consideration of certain tailless forms in 

 v/hich the eggs are less numerous and of larger size, containing 

 indeed so much food-yolk that there is no necessity for early 

 hatching, and the young animals begin their free existence either 

 as advanced tadpoles which 

 have already lost their gills, or 

 else in the adult form. There 

 is often some special provision 

 for the care of such eggs during 

 their development, and a com- 

 parison may well be inade with 

 those fishes which exert a cer- 

 tain amount of parental care 

 (see p. 426). In the simplest 

 case the eggs are simply de- 

 posited in damp places, as in a 

 Japanese species i^Rhacophorus 

 Schlegelt) of tree-frog, where 

 the female digs a hole near a 

 pond or ditch and lays her eggs 

 in it, also taking care to provide 

 a supply of air by working up 

 the jelly of the spawn into a 

 sort of frothy mass by means 

 of her hind-feet. Tadpoles hatch out from these eggs later on. 



A pretty little West Indian tree-frog {Hy lodes Martinicensis, 

 fig. 963) lays about a score of large eggs upon a leaf, very often 

 in the sheltered angle close to the stem. They are imbedded in 

 a frothy mass of jelly. While development is going on it is said 

 that the mother remains on guard not far off Minute frogs of 

 about one-fifth of an inch in length emerge from the eggs in about 

 three weeks. The tadpole stage is thus passed through before 

 hatching, and it is noteworthy that there is a certain amount of 

 " hastening of events " in the development, since gills and gill-slits 

 do not make their appearance, there being in fact no need for 

 them. 



Fig. 963. — Development of a West Indian Tree -Frog 

 [Hylodes Martinicensis). A and B, Eggs containing em- 

 bryos seven and twelve days old; c, just-hatched Frog; 

 D, adult male. 



