General Account of the Ithacan Anura. 



17 



firmer jelly envelopes. They are the first six to breed and are mainly 

 through ovulation by the middle of May. 



The egg-masses are spherical in the wood-frog and in the pickerel- 

 frog; plinth-like in the meadow-frog; spiral in the toad; a surface film 

 in the tree-toad, the green-frog, and the bullfrog; a submerged film or 

 sphere in the swamp cricket-frog, and single eggs in the peeper. In all 

 the nine species except the peeper, several eggs are laid at each sexual 

 period (i. e., at each emission and fertilization). Five species lay the 

 whole complement in a few minutes. In the other four (the peeper, 

 the toad, the swamp cricket-frog, and tree-toad) several hours may be 

 consumed in completing the ovulation, and the females do not keep the 

 same position throughout the whole process. The egg-complements 

 range from 800 in Hyla pickeringii to 20,000 in Rana catesbeiana. 

 A summary of the egg characters of each species follows in the accom- 

 panying key (page 18.) 



FIG. 1. INDIVIDUAL EGGS. X-4. 



A. Egg of Bufo lentiginosus americanus in two jelly-envelopes or tubes, the inner of which is 



divided by cross partitions. 



B. Egg of Rana palustris. Inner envelope and vitellus of same size as egg of Rana pipiens 



(G) but outer envelope smaller. 



C. Egg of Hyla pickeringii. The one envelope and the vitellus together appear the dupli- 



cate of the egg of Hyla versicolor (E) when it is stripped of its outer envelope. 



D. Egg of Rana clamata. Unlike the egg of Rana catesbeiana (F), it has an inner enve- 



lope and this is elliptical, not round as in most Anuran eggs. 



E. Egg of Hyla versicolor. The outer envelope often ragged in outline. 



F. Egg of Rana catesbeiana. Unlike the other four Ranas, it has no inner envelope. 



G. Egg of Rana pipiens. Compare B. 



H. Egg of Rana sylvatica. It has the largest vitellus of the eight species figured and larger 

 envelopes than the confusing B and G. 



