92 The Wood-frog, Rana sylvatica LeConte. 



degrees. Thereafter, the temperatures were below 52 degrees, with 

 one exception. An average of 22 water-temperatures for this year 

 gives 48 degrees. In 1910 the species began at a water-surface temper- 

 ature of 57 degrees or water-bottom record of 50 degre3s. Whan the 

 spawning reached the crest, these were respectively 60 and 59 degrees. 

 From the crest onward to end of spawning the water-surfaces ranged 

 from 55 to 68 degrees; the water bottoms, from 53 to 60 degrees; the 

 averages for the whole season were water-surfaces 60 degrees, watei- 

 bottoms 56 degrees. 



In 1911, the water- surf aces averaged 53 degrees, the water-bottoms 

 51 degrees; the crests in three ponds came at 50, 51, 70 (water-surfaces) 

 and 48, 51, 67 degrees (water-bottoms) respectively. In this year 

 maximum and minimum records were kept, and no minimum below 



42 degrees was recorded, the maxima ranging from 44 to 62 degrees, 

 the average being 54 degrees. A grand total of all our water-surface 

 and water-bottom records show averages of 56 and 53 degrees respec- 

 tively. 



To recapitulate: When the maximum air-temperatures reach 41 to 



43 degrees, or average 53 to 58 degrees, we may go out with some 

 expectation of finding the wood-frogs spawning, provided the water- 

 temperatures are at least 41 to 48 degrees. At the latter temperature 

 the spawning reaches its height usually at about 53 to 60 degrees. 



THE EGG-LAYING PROCESS. 



Most of the egg-complements are laid at night, yet we have frequent 

 instances of day-laying, both in the laboratory and in the field. In 

 the former they have laid throughout the day; in the field we have 

 numerous indications of it. According to our record, day-laying in the 

 field seems to occur in the early morning or late in the afternoon. 

 On April 10, 1911, between 12 h 30 m and 8 p. m., a fully expanded bunch 

 was found which must have been laid before 7 p. in.; on March 28, 

 1907, a pair was observed leaving an egg-mass at 8 a. m.; and on April 

 6, 1908, a female was beginning laying at ll h 30 m a. m. 



This species is gregarious at this season. Where the first bunch 

 of eggs is laid, one is quite certain to find others depositing their com- 

 plements later. In this way the whole egg-content of a large pond may 

 frequently be massed in a small limited area (Plate xxi, Fig. 1). In 

 1906 one area of 6 bunches was recorded. In 1907 (March 29) there 

 were 10 bunches in an area 8 by 8 inches; about a foot north was another 

 area of the same dimensions with 8 bunches; on the subsequent day 

 the interval was filled with 10 more, thus making 28 bunches in an 

 area 28 by 8 inches. In one instance, one bunch of eggs was found and 

 a stake was driven near it as a marker; the next morning it was hardly 

 to be seen, for 9 new masses had been laid about it. In 1908, on April 

 8, an area 18 by 10 inches possessed 37 bunches. In another pond, on 

 April 13, one small Alisma plant, not yet above the water's surface, 



