1868.] 193 [Allen. 



icanus appeared, and a very few pairs of Scaphiopus Holhrookii were 

 observed spawning. 



"April 16th. At 8 A. M. air 60°; running water 50°; still water 

 56°. At 7 P. M. air 60°; running water 52°; Stillwater 58°-62°. 

 Day fine and warm. This evening Bii/o americanus spawning in great 

 numbers, in water varying in temperature from 56°-62°." 



At this date I was called away for a few days, and my record 

 ceases. I had intended to note the length of time occupied in hatch- 

 ing the eggs of the different species, with at least three daily observa- 

 tions on the temperature of the water surrounding them; the rapidity 

 of development, as I found, and as would be expected, varies with the 

 temperature of the water.^ Imperfect as these memoranda are, they 

 show that Hyla Pickeringii, usually the first frog we hear in spring, 

 is the species that continues active at the lowest temperature; and 

 that Rana sylvatica will bear almost as great a degree of cold. Ac- 

 cording to observations made last spring, and partially recorded above, 

 I found H. Pickeringii sometimes piping till the temperature of the 

 water had fallen to 38°, and once when that of the air was 31°; but 

 they were never observed in numbers when the water was colder than 

 from 45° to 42°. I never saw or heard R. sylvatica when the water was 

 colder than about 50°, or the air in the shade below 34°. With a rise 

 of a few degrees only above these points in the temperature of the 

 water, particularly at midday, both their numbers and activity would 

 be considerably increased. Ordinarily I found a difference of about 10° 

 in the temperature at which these species retire from the surface, — R. 

 sylvatica disappearing at 54° to 48°, and Hyla Pickeringii at 44° to 38°. 



There were several excessively warm days at the time of the 

 first appearance of these species (April lst-5th), when the water sud- 

 denly reached a maximum temperature of above 60°, and during 

 this time R. sylvatica commenced spawning. Seven or eight days 

 of freezing weather immediately succeeding intercepted their opera- 

 tions till the 15th, when the temperature of the water again reached 

 60° to 65°. At this time H. Pickeringii again commenced spawning; 

 R. sylvatica was again seen pairing, and most of the other Ranee were 

 observed, as well as Bufo and Scaphiopus. The embryos in the ova 

 of R. sylvatica, laid April 3d, were not much advanced two weeks 



1 Since the above was written I have met with an account of Hogg's experi- 

 ments on the influence of light and heat on tlie rapidity of the hatching and meta- 

 morphosis of the larvae of frogs, from which it appears that the former, as well 

 as the latter, may have considerable influence. 



PROCEEDINGS B. S. N. H.— VOL. XII. 13, JANCAKY, 1869. 



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