AMPHIBIANS 185 



2. The Eggs and Larvae. In the identification of the freshly laid 

 egg-masses of frogs and toads the first feature to be examined is the form 

 and condition of the jelly in which the eggs are imbedded and its location 

 in the water; the time of the year when the eggs are found is also of 

 importance, whether in the early spring, the later spring or the summer. 

 The egg is a spherical body ranging from 0.9 mm. to 2.4 mm. in diameter, 

 in the different species, which has two distinct surfaces, the dark, pig- 

 mented upper surface, or animal pole, and the white or yellow under 

 surface, or vegital pole; the pigmented portion is much the larger in 

 extent. The egg is surrounded immediately by a spherical envelope of 

 jelly, inside of which and next to the egg is, in most species, a second or 

 inner envelope. 



Key to the Eggs of some of the common Eastern Frogs and Toads 



ai Eggs laid in a single row within a long spiral chord of jelly 

 which lies on the bottom or is looped around plants or 

 sticks; diameter of chord 3.4 to 4 mm.; number of eggs 

 4,000 to 7,000; season of egg laying April, May and June. Bufo americanus. 

 a2 Eggs laid in a mass or singly. 



bj Eggs laid in a firm consistant mass around sticks, twigs, 

 etc., or free, and usually near the surface of the water. 

 Ci Inner jelly envelope of egg small and distinct. 



di Vegital pole of egg yellow; animal pole brown; 

 egg mass globular; season of egg laying April 

 and first half of May; number of eggs 2,000 to 



3,000 Rana palustris. 



do Vegital pole of egg white; animal pole brown; 

 egg mass elongate; season of egg laying latter 

 part of March to middle of May; number of 



eggs 3,500 to 4,500 Rana pipiens. 



Co Inner jelly envelope of egg large and indistinct, or 

 apparently absent; vegital pole of egg white; ani- 

 mal pole black; egg mass globular; season of egg 

 laying middle of March to end of April; number 



of eggs 2,000 to 3,000 Rana sylvatica. 



bo Eggs laid in large loose masses or in small bunches or 

 singly. 

 Ci Eggs laid in large loose masses at or near the surface 

 of the water; vegital pole of egg white; animal pole 

 black, 

 di Eggs laid usually in one continuous film, one or 

 two eggs thick, on the surface of the water, 

 among plants; season of egg laying latter part 

 of May to middle of August; inner jelly enve- 

 lope of egg distinct, elliptical in shape; number 

 of eggs 3,500 to 4,000 Rana damitans. 



