46 THE BIOLOGY OF THE FROG chap. 



bunches of Amblystoma, for this Urodele also lays its eggs 

 very early. 



" Somewhat later two species of tree frogs appear in the 

 small pools in the woods, generally in quite small, and, there- 

 fore, during the day often quite warm, puddles ; sometimes 

 in the same pools as the wood frogs, oftener in the ditches 

 by the side of the road. These two frogs are Hyla picker- 

 ingii and Chorophilus triseriatus. The eggs of these species 

 are very similar, and I know of no certain method of distin- 

 guishing the one from the other. The bunches are small, 

 attached to bits of grass, or lie simply on the bottom, and 

 each bunch contains from five or six to fifteen or twenty 

 eggs. I have the following record of the times at which the 

 eggs were found': Hyla, March 9, 10, 13; April 5, 1890. 

 Chorophilus, February 23, 1891 ; March 13 and 24, 1890. 



*' The eggs of Rana halecina are found still later, some- 

 times in the same localities as the wood frogs, oftener in pools 

 in the open ground quite away from the woods. The follow- 

 ing are the records: March 25, April 15, 1890. Eggs of 

 Biifo kutiginosiis were reported from the same region on 

 April 14, 1890, and April 5 and 6, 1891." 



Duration of the Breeding Period. — The duration of 

 the breeding period, like the time of its first appearance, is 

 very dependent upon external conditions, especially tempera- 

 ture. The period of copulation, or the time during which 

 males may be found clasping the females, often considerably 

 exceeds the period between the first and last deposition of 

 eggs. This is due to the fact that the males seize the 

 females often several days before the first eggs are laid. 

 According to Fischer-Sigwart's observations of Ratiafusca^ 

 the females may lay eggs, if the weather is warm, three days 

 after the beginning of copulation ; but in cold weather the 

 laying may be deferred for twenty or thirty days. The dura- 



