70 ALBERT HAZEN WRIGHT. 



already mated in nature. These were usually captured on night 

 trips and were immediately taken to the laboratory, By the 

 next morning an egg complement was ordinarily recorded. In 

 this way a check was established upon the identification of eggs 

 deposited in nature. 



The measurements are based on fresh eggs none of which is 

 beyond the fine morula stage. The color characters of the vitel- 

 lus were taken at the time of oviposition with 7 species and not 

 later than 6 or 8 hours after oviposition with the other species. 

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

 accompanying key : 



Key to the Eggs of Ithaca Anura. 



A. A single row of eggs within a long spiral string of jelly looped about plant stems, 

 sticks or resting upon the bottom ; vitellus diameter i. 0-1.4 mm.; inner envelope 

 diameter 1.6-2.0 mm.; outer envelope diameter 3.4-4.0 mm. Egg complement, 



4,000-7,000. Season at Ithaca, April 20- July £u/o leniiginosus americanus. 



AA. Deposited singly or in a mass. 



B. Deposited in a firm consistent mass enveloping grass stems, twigs, etc., or 

 free ; submerged ; often 15-20 bunches within an area of a few square feet. 

 C. Small distinct inner envelope evident to the naked eye, 2.3-3.0 mm. 

 D. Vegetative pole yellow ; animal pole brown ; mass globular ; vitel- 

 lus 1. 6-1. 9 mm.; outer envelope, 3.6-5.0 mm. Egg complement, 



2,000-3,000. Season, April 25-May 15 Rana palusirh. 



DD. Vegetative pole white ; animal pole black ; mass plinth-like ; 

 vitellus 1. 6-1. 8 mm.; outer envelope 4.2-6.0 mm. Egg complement, 



3,500-4,500. Season, April lo-May 15 Rana pipiens. 



CC. Large inner envelope apparently absent, evident only under the lens, 

 3.6-5.8 mm.; vitellus 1. 8-2. 4 mm.; outer envelope 5.2-9.4 mm.; mass 

 globular ; vegetative pole white ; animal pole black. Egg complement, 



2,000-3,000. Season, April 1-30 Rana sylvatica. 



BB. Deposited not in a hard consistent mass. 



C. In small bunches or attached singly ; vitellus, .9-I.2 mm. 

 D. Outer envelope loose, 4.0-7.8 mm. 



E. Inner envelope, 1.6-2.0 mm.; vegetative pole yellowish; in 

 small bunches (4-25) usually floating at the surface of the 

 water, either attached to vegetation or free ; outer envelope, 4.0- 

 6.0 mm. ; vitellus, I. i-i. 2 mm. Egg complement, 1,500-2,000. 



Season, May 20-July i Hyla versicolor. 



EE. No inner envelope ; vegetative pole white ; in bunches (20- 

 100) usually attached beneath the surface of the water ; outer 

 envelope usually 5.0-7.8 mm., rarely 3.0 mm.; vitellus .9-1.2 

 mm. Egg complement, 500-800. Season, March 20-April 15. 



Chorophilus triseriatus. ^ 

 DD. Outer envelope firm, 1.4-2.0 mm. ; vegetative pole never yellow ; 



^ Introduced at Ithaca in April, 1909. 



