General Account of the Ithacan Anura. 



19 



THE HATCHING PERIOD. 



The hatching period depends mainly upon the season and its temper- 

 ature. The wood-frog, meadow-frog, and peeper, which breed earliest, 

 may require from 24 to 12 or 11 days. They have submerged eggs, and 

 not infrequently the ponds freeze over after they are laid. The pickerel- 

 frog, which breeds in the latter part of April, lays its eggs in deeper water 

 than the toad. Usually its eggs require from 21 to 1 1 days for hatching, 

 while the toad, which lays in the shallows (more influenced by air-tem- 

 peratures), needs only 12 to 3 days. In these five forms, the eggs are 

 submerged, though the position of the toad's eggs may at times approach 

 the surface of the water. In the three forms which breed after May 25, 

 the eggs are laid on the surface of the water, and are partially influenced 

 by the higher air-temperatures. In 

 this group (the green-frog, the tree- 

 toad, and the bullfrog) the eggs hatch 

 in 6 to 3 days. It was found that irre- 

 spective of species the eggs of all the 

 eight forms would hatch in 4 or 5 days 

 under the laboratory temperatures of 

 70 to 65 degrees. This explains the 

 great differences in hatching period between the earliest and latest 

 breeders and between immersal early eggs and buoyant late eggs. 

 From a consideration of all the hatching data, the above table, which 

 applies to all the eight species, is constructed. 



THE LARVAL PERIOD. 



According to the length of the larval period, the species of this 

 region fall into two groups: those which transform during the season 

 in which their eggs are laid and those which require one or more years 

 for their development. The data are as follows: 



The forms with short larval periods generally complete egg-laying by 

 July 1. Their tadpoles do not have to reach the transformation-size 

 required of the two species with long larval periods. In the former 

 group the average sizes of transformation range from 9.6 to 24 mm.; 



