18 General Account of the Ithacan Anura. 



KEY TO THE EGGS OF ITHACAN ANURA. 



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



or resting upon the bottom; vitelline diameter, 1.0 to 1.4 mm.; inner 

 envelope diameter, 1.6 to 2.0 mm.; outer envelope (outer spiral 

 string of jelly) diameter, 3.4 to 4.0 mm. Egg-complement, 4,000 

 to 7,000. Season at Ithaca, April 5 to July 25; the average first 

 date, April 23 Bufo lentiginosus 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 to 20 bunches within an area of a few square feet. 



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



D. Vegetative pole, yellow; animal pole, brown; mass globular; vitellus, 

 1.6 to 1.9 mm.; outer envelope, 3.6 to 5.0 mm. Egg-complement, 

 2,000 to 3,000. Season, April 6 to May 18; the average first date, 

 April 23 Rana palustris 



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

 1.6 to 1.8 mm.; outer envelope, 4.2 to 6.0 mm. Egg-complement, 

 3,500 to 4,500. Season, March 29 to May 15; the average first date, 

 April 11 Rana pipiens 



CC. Large middle envelope apparently absent, slightly evident under the lens, 

 3.6 to 5.8 mm.; vitellus, 1.8 to 2.4 mm.; outer envelope, 5.2 to 9.4 

 mm.; mass globular; vegetative pole, white; animal pole, black. 

 Egg- complement, 2,000 to 3,000. Season, March 19 to April 30; 

 the average first date, April 4 Rana sylmtica 



BB. Deposited not in a hard, consistent mass. 



C. In small bunches or attached singly; vitellus, 0.9 to 1.2 mm. 

 D. Outer envelope loose, 4.0 to 7.8 mm. 



E. Middle envelope, 1.6 to 2.0 mm.; vegetative pole, yellowish or cream; 

 in small bunches (4 to 25) usually floating on the surface of the water, 

 either attached to vegetation or free; outer envelope, 4 to 6 mm.; 

 vitellus, 1.1 to 1.2 mm. Egg-complement, 1,500 to 2,000. Season, 



May 10 to June 17; the average first date, June 2 Hyla versicolor 



EE. No middle envelope; vegetative pole, white; in bunches (20 to 100) 

 usually attached beneath surface of water; outer envelope usually 5.0 

 to 7.8 mm., rarely 3.0 mm. ; vitellus, 0.9 to 1.2 mm. Egg-complement, 



500 to 800. Season, Mar. 20 to Apr. 15 Chorophilus triseriatus 



DD. The one envelope firm, 1.4 to 2.0 mm.; vegetative pole, never yellow; 

 single or in small bunches (4 to 12) attached to grass beneath the 

 surface of the water; vitellus, 0.9 to 1.1 mm. Egg-complement, 

 800 to 1,000. Season March 30 to May 10; the average first date, 

 April 10 Hyla pickeringii 



CC. In large loose masses; vegetative pole, white; animal pole, black; vitellus, 

 1.2 to 1.7 mm.; at or near the surface of the water. 



D. Usually one continuous film, 1 to 2 eggs thick, on the surface of the water, 

 the film's diameter being seldom one foot; middle envelope distinct, 

 elliptical, 2.8 to 4.0 mm.; egg-mass usually attached to or amongst 

 vegetation. Egg-complement, 3,500 to 4,000. Season, May 23 to 

 August 10; the average first date, June 7 Rana clamala 



DD. Either a film 1 to 2f feet in diameter or a stringy frayed widespread mass; 

 attached to twigs or sticks; almost invariably among brush, and at 

 or near the surface of the water; no middle envelope. Egg-comple- 

 ment, 12,000 to 20,000. Season, June 16 to July 10; the average 

 first date, June 28 Rana catesbeiana 



