12 General Account of the Ithacan Anura. 



Whenever one or more mated pairs were secured on my night trips, 

 I returned immediately to the laboratory, being reasonably certain 

 of an egg-complement by the next morning. With 75 or more mated 

 pairs (Bufo not counted) captured afield, this seemed the general rule. 

 The two species which occasionally did not lay by the next morning 

 were Rana palustris and Rana pipiens. In Rana palustris, as many as 

 14 days have transpired before ovulation. For six years, I have seen 

 the mating of this species in areas where there were no eggs or very few. 

 The next day after the record of such first matings in great numbers, 

 countless bunches were recorded, implying a day or less in the embrace. 



Ovulation without apparent mating has been recorded for three 

 species. On April 28, 1906, an isolated female Rana palustris laid in an 

 aquarium, no male being present; the same was recorded for Bufo I. 

 americanus and Rana clamata. In each of these cases the whole com- 

 plement was quickly laid and did not extend far beyond the period 

 normally required for the species, as is often the rule with the delayed 

 laying in captive pairs. 



When mated, if the male be removed, the female often lays. With 

 a member of the genus Hyla, an experiment was tried as follows : On 

 the evening of June 17, 1907, two mated pairs of Hyla versicolor were 

 captured. One pair was allowed to remain in the embrace; the other 

 was separated. The next morning, both the attended and the un- 

 attended females had laid. Later, a mated pair was separated and the 

 female was placed over night in a dry jar, but the next morning eggs 

 were found, though no water was present. Three years later the same 

 experiment was made with three pairs of Bufo with identical results. 

 Even when the conditions are very untoward, the female often ovulates; 

 e. g., a pair of meadow-frogs escaped from a jar, traveled from a third 

 floor to the first floor, and laid their egg-complement on the first floor 

 staircase. Absence of mating, separation from mates, or presence in 

 air (not water) can not prevent ovulation when once the process has 

 reached an advanced stage. Apparently, the female must ovulate 

 whether she would or not. 



The spawning periods of the various species were considered from 

 the following points of view: average date; range of spawning period; 

 average interval and range of intervals between first appearance and 

 first ovulation; the beginning and average maximum air-temperatures 

 of ovulation; and the beginning and average water-temperatures of 

 ovulation. The data will be found in the table at the top of the fol- 

 lowing page. In the spawning record there is a close approximation to 

 the grouping of the first appearance. The same forms are associated, 

 except that the last three species which appear in three distinct groups 

 are here assembled in one. 



The first three to appear, namely, the wood-frog, the peeper, and the 

 meadow-frog, proceed at once to pair and ovulate. They appear, on 



