The Bullfrog, Rana catesbeiana Shaw. 83 



clamata and catesbeiana is that those of catesbeiana do not possess 

 a distinct middle envelope, while those of clamata do. Furthermore, 

 this middle envelope in the eggs of the green-frog is elhptieal, not round, as 

 in the species of Rana which possess middle envelopes. (Text-figure If.) 



THE HATCHING PERIOD. 



Four bunches of eggs laid June 24, 1906, were ready to hatch June 28. 

 The maximum air-temperatures ranged from 72 to 86 degrees or aver- 

 aged 80 degrees. The water-bottoms were from 65 to 69 degrees or 

 averaged 67 degrees. In 1907 a complement was laid July 9; on July 

 10 a part of the complement was brought into the laboratory, and by 

 July 13 they were hatched; the remainder in the pond hatched July 13, 

 when the maximum air-temperatures had been from 68 to 83 degrees 

 or had averaged 76 degrees. The water-bottoms were from 65 to 74 

 degrees. In all four instances there was a period of 4 days required 

 for hatching, the effective temperatures no doubt being somewhere 

 between those of the water-bottoms, whose averages were 67 to 71 

 degrees, and the air-maxima, whose averages were 76 to 80 degrees. 

 In another instance we have evidence which quite certainly indicated 

 a period of less than 4 days. During this period the water-bottoms 

 averaged 75 degrees and the water-surfaces averaged 86 degrees or 

 ranged from 72 to 95 degrees. 



The range of water-bottoms in all these records was from 65 to 75 

 degrees. None of the air-maxima descended below 68 degrees, and 

 their averages were from 76 to 86 degrees. An intermediate range 

 between the two sets, namely, 70 to 80 degrees, very well represents 

 the prevaihng surface-temperatures through the hatching period. 



THE MATURE TADPOLE. 



Two year old tadpole: Length of body in tail 1.56 to 2.15, average 

 1.8. Width of body in its own length 1.1 to 1.6, average 1.3. 

 Nostrils equidistant from snout and eye. Eye nearer the snout than 

 the spiracle. Distance between the nostrils in the interorbital space 

 1.75 to 2.2, average 1.96, mode 2.0; in mouth 0.95 to 1.16, average 1.07. 

 Depth of the tail in the length of the tail 2.4 to 3.5, average 2.8. Mus- 

 cular part of the tail at its base contained in depth of tail 1.4 to 1.9, 

 average 1.8. Distance from spiracle to base of the hind legs 1.08 to 

 1 .44 in the distance from the spiracle to the snout, average 1 .26. Mouth 

 contained 1.3 to 2.1 times in the interorbital distance, average 1.73. 

 Greatest length, 145 mm. Greatest length of body, 45 mm. Greatest 

 length of tail, 100 mm. Greatest depth of tail, 38 mm. 



Coloration of body (Plate ix, Fig. 1a) : Background of back ohve green, 

 closely overlaid with fine yellow dots. Back conspicuously marked with 

 dark spots, which become scanty on the slightly (bronzy) iridescent 

 sides. Eye bronze. Venter is straw or maize yellow, with a few greenish 

 spots toward the sides and sometimes in the region of the throat. 



