208 VERTEBRATA 



frogs and the Amblystoma appear as dark bodies of pin- 

 head size imbedded in a mass of clear, jellylike albumen. 

 The eggs of the toad are deposited in strings. The newt 

 fastens its eggs singly within little tufts of aquatic leaves, 

 while Plethodon hides its eggs under stones arid logs on 

 land. 



The time of year when the various species breed extends 

 from March to October. The eggs of the Amblystoma and 

 the leopard frog are found as soon as the snow melts in 

 the spring, while the green frog and brown frog spawn in 

 April. In May or June the common tree frog attaches its 

 eggs in small masses to stems of weeds and grass in shallow 

 pools, and the bullfrog seldom spawns before July. The 

 toad scatters its strings of eggs over the stones and brush 

 in any small pool or pond during late April and early May. 

 The breeding season of the newts extends from April to 

 July, and some of the large urodels lay their eggs in the 

 autumn. 



The young of the amphibians are known as larvce or tad- 

 poles. They dwell in the water and breathe by means of 

 gills. In the case of frogs and toads, the food consists 

 largely of vegetable matter, which fact accounts for the 

 great length of the intestine in these forms. The intestine 

 of the adult feeding on animals is not one fourth as long as 

 that of the larva. The Amblystoma larvaB feed on aquatic 

 insects, such as mosquito larvae and pupae, and therefore 

 have a short intestine, as nutrition is easily secured from 

 animal matter. The length of the larval period varies in 

 the different species. For the toad it is usually about two 

 months, while in some frogs it lasts six months and in 

 others more than a year. Many of the salamanders pass 



