AMPHIBIA 225 



knowledge of danger. Romanes records an instance of a pel 

 frog which would come when his name, "Tommy," was called, 

 no matter at what time of day, though fed only at morning, and 

 another instance of a toad kept as a pet for thirty-six years, 

 which knew all of his friends. In either case, the knowledge 

 might have been gained, at least in part, by sight. 



The eye has no lids in the lower forms, and is degenerate in 

 the Pro' tens, which lives in caves (see Fig. 189), and in some 

 Gymnophi'ona. Most of the Anura have an upper lid, but no 

 lower one. There are no tears. The "flying tree-toad" has 

 large owl-like eyes (see Fig. 195), so that it can see as i'ar as it 

 leaps. Frogs are able to project the eyes upward to give greater 

 range of vision. When the mouth is inflated the eyes are pushed 

 forward, since there is no partition between the eyes and mouth. 

 It is well known by boys that frogs recognize bright colors, and 

 it has been proved by experiment that they can distinguish red 

 from white. 



Development. — The eggs of Anura, which consist of the 

 yolk enclosed in a mass of jelly-like matter, are not surrounded 

 by a shell. They are usualy deposited in masses (frogs) or in 

 strings (toads), and then left to hatch by the heat of the sun. 

 The little tadpole has a small sucking mouth and a slender active 

 tail. The branched gills soon grow out on the sides of the neck, 

 but are later replaced by internal gills, when the water passes 

 in through an opening on each side of the neck. The tail is 

 gradually absorbed, the legs develop, the holes on the sides of the 

 neck close, and the limbs develop underneath the skin, the hind 

 legs coming out first in the frog forms, but in all others it is the 

 fore limb that first shows. ^ Meanwhile "the tadpole ceases to 

 feed, the whole intestinal canal is voided of its contents, and, by 

 histolysis, is entirely rebuilt, becoming wider and shrinking 

 to about one-sixth of its original length, undoing thereby the 

 spiral, preparatory for the coarser food, which consists of in- 

 sects, worms,"- and any live animals it can capture. 



Care of the Young. — Usually the parents take no care of the 

 young, but there are some interesting exceptions. The little 

 South American frog {Rhinoder'ma dar'wini) carries the eggs in 



' Baskett, " Story of the Amphibians and Reptiles," p. 34. 

 2 Gadow, p. 61. 



