I 



THE OVUM IN THE AMPHIBIA. 1/3 



garis, among the'dnoura ; and the Triton palustris, Lissotriton punctatm and L. pal- 

 mipes, among the Water Newts, the Urodela. Neither SPALLANZANI, PREVOST and 

 DUMAS, nor RUSCONI, to whose observations I shall have frequent occasion to refer, 

 mention the species they have examined. SPALLANZANI has given only the popular 

 names of his animals, but RUSCONI has given a figure of his, which appears to have 

 been Rana esculenta, and as the description he has given of the ovum of this species 

 agrees with the description given by PREVOST and DUMAS, it is probable that the 

 species they employed was the same. 



The Ovarlum Ovum. When the frog, Rana femporaria, is examined in the autumn, 

 after it has ceased to feed, and is preparing to retire to its winter quarters, the ova 

 within it have already attained to more than two-thirds of their ultimate dimensions 

 before leaving the ovaries, and have begun to distend the abdomen. They remain in 

 this state through the greater part of the winter, while the frog is hybernating, as 

 Professor BELL remarks*, in the mud at the bottom of ponds and stagnant waters. 

 But as the spring approaches, and the animal is aroused from its lethargy by increased 

 temperature, the ova then rapidly acquire their full development. A female frog, taken 

 at the end of September, with her body enlarged with ova, was confined in water in 

 a cold room, undisturbed through the winter, excepting only at intervals of examina- 

 tion. The weather being mild, and the temperature of the room during October 

 and November being sometimes at or but little below 50 FAHR., the frog remained 

 active, and came frequently to the surface to respire. In December the tempera- 

 ture sunk to below 40 FAHR., when the frog became lethargic, and scarcely changed 

 its place at the bottom of the water during nearly a fortnight, while the temperature 

 was almost stationary, and ranged only from 35 FAHR. to 37 FAHR. On the 10th of 

 January, when it had again risen to 40 FAHR., and that of the water to 37' 5 FAHR., 

 the animal was still submerged and motionless ; but on sudden exposure to the light 

 of a candle it crept languidly, and almost imperceptibly, to a distance of about two 

 inches, and again became quiet. On the 26th of January the temperature of the 

 room had risen gradually and continuously to 52 FAHR., and that of the water to 48 

 FAHR., but the frog remained submerged and perfectly quiet with its eyes partially 

 closed. Although it was not cognizant of any object by sight, the irritability of its 

 body was now much increased, as it moved instantly when touched ever so lightly, 

 but quickly relapsed into its previous state of rest. On the morning of the 1st of 

 February, the temperature being then 48 FAHR., it was still submerged and motionless, 

 but in the evening, when the warmth was increased to 52 FAHR., I found it with its 

 nostrils only above the surface of the water, and evidently beginning to respire freely, 

 but its eyes were completely closed. When the light of a candle was suddenly cast 

 upon it, the eyes were slowly opened, but its body remained immoveable. On the fol- 

 lowing day, February 2, it was evident that its hybernation had been brought to a 

 close, as it was then active, with its head out of the water, and its eyes widely open, 



* History of British Reptiles, 1832, p. 89. 



