The Tree-toad, Hyla versicolor LeConle. 49 



10 seconds, as there was between the second and the third. When the 

 third was completed, the pair rested for 2 minutes. The egg-laying 

 might last an hour or more. 



The female would become restless just before each sexual period. 

 The fertilization took place beneath the surface of the water, when the 

 female's body was at an acute angle to the surface and the dorsum of 

 her head was above the water. After each fertilization the female 

 would raise her vent above the water and lay 18 to 25 eggs. There 

 would be three or four slight movements of the hind legs with each 

 emission. In certain instances, after egg-laying had been completed, 

 the pair remained in the embrace several hours. 



THE EGGS. 



In the field (Plate i, Fig. 2o) the first eggs found were secured May 

 27, 1906. Around a Potamogeton plant were three isolated patches of 

 eggs numbering 6, 10, 14 respectively. Shortly after, they became 

 common among the tall grasses and plants in the marshes, in mid-pond, 

 or in the open around the edges of the ponds. They float and may often 

 be seen at a distance of several feet because of the excessive number of 

 air-bubbles interspersed with each small bunch of eggs. 



During 1906 and 1907 eight different females laid in the laboratory. 

 An estimate of one egg-complement (after a count of 400) was 1,800 

 to 2,000 eggs. A conservative estimate could not put the normal 

 number below 1,000. 



The egg-packets (4 to 25) may be 6 to 12 inches apart, or only an 

 inch or less. (Plate vn, Fig. 4; xiv, Fig. 4). Sometimes these groups 

 are arranged at more or less definite intervals, by means of which the 

 approximate path of the pair can be traced. They are more frequently 

 found attached, but often become free later. Occasionally the eggs are 

 not found at the very surface. Such are attached eggs, and in these 

 cases they were doubtless laid at the surface, but were later submerged, 

 due to a change in level of water after rain-storms. 



The egg-mass is loose in consistency. Each individual egg has a 

 yellowish vegetative pole and a brown animal pole ; the outer envelope 

 is ragged around its edges and has a diameter of 4 to 6 mm., the average 

 5.2 mm., the mode 5.0 mm. The vitelline envelope is from 1.6 to 2 mm. 

 in diameter, average 1.7 mm., mode 1.7mm. The vitellus diameter is 1.1 

 to 1.2 mm., the average and mode both being 1.2 mm. (Text-figure 1 E.) 



THE HATCHING PERIOD. 



Eggs laid in the laboratory and kept under a temperature of 66 to 

 70 degrees hatched in 5 days. In May 1911 some eggs hatched in 4 

 days where the water-surface averaged 70 degrees or more for the 

 period. On June 13, 1911, some eggs were found which were in the 

 yolk-plug stage; they were probably laid June 11 or 12; on the 14th 

 they approached hatching; on the 15th they hatched, giving 4 or 5 days 



