174 MR. NEWPORT ON THE IMPREGNATION OF 



and perfectly alive to external objects, as when the hand was slowly approached it 

 withdrew beneath the water. The temperature at this time was 53 FAHR. During 

 this period of hybernation the frog became slightly emaciated, and its abdomen, 

 instead of being more enlarged, was somewhat diminished in bulk, a good proof 

 that during the inactivity of the respiratory and circulatory functions, the secretory 

 also are lessened, and the development of the ova is arrested. But although no food 

 was supplied to the frog at this time, and none probably is taken by the creature in its 

 natural haunts, as at the time it comes forth but few of the objects on which it feeds 

 are abroad, its body soon became enlarged, showing that the ova were then rapidly 

 attaining their full development. Between the 2nd and 22nd of February the tem- 

 perature of the room was occasionally as low as 42 FAHR., yet the creature remained 

 active beneath the water, without relapsing into its previous state of hybernation. 

 It only continued longer beneath the surface without rising to respire. At this period, 

 having found that some frogs in their natural haunts had already come forth, I 

 removed the subject of these observations also from the water to a damp locality, and 

 on the following day found it greatly changed in appearance. While confined in the 

 water it was of a dull dirty brown colour, but some hours after its removal it cast 

 its tegument, and changed to a bright yellow, with the usual brown markings, and 

 had increased in size, both in its body and limbs. 



The conclusion to which these circumstances seemed to lead was, that quickly after 

 the frog leaves its hybernaculum, it casts its tegument as the insect escapes from its 

 puparium, and acquires new vigour, while the ova are attaining their full growth. 

 The Toad undergoes a similar change. About a fortnight later in the season than 

 the Frog, I have seen many toads in a shallow ditch of slow moving water in the act 

 of casting their dark brown tegument, and acquiring one of a greenish yellow. 



On examining several frogs taken from their natural haunts, I found them in, as 

 nearly as posible, the same state of development with regard to the ova, judging from 

 external appearance, as the specimen I had watched through the winter. A few had 

 just paired, but the majority were still single. On opening the bodies of the latter, 

 I found the ovaries greatly enlarged, and the ova apparently ripe, but still contained 

 in the ovisacs. 



It is at this period, therefore, immediately after hybernation, and before the ova 

 have left the ovarfes, that the condition of the ovum is a matter of great interest with 

 reference to the structure and contents of the germinal vesicle, the period at which 

 the vesicle is changed or disappears, and the circumstances under which the ovum 

 escapes from the ovary, and is received into the oviduct. 



The Germinal Vesicle. The fate of the germinal vesicle in the matured ovum is 

 still a matter of doubt. Previous to the embryological researches of Dr. MARTIN 

 BARRY, it was usually believed that the vesicle entirely disappears before or at the time 

 of fecundation of the ovum. But this view was combated by the author named, who, 

 quoting the opinions of previous inquirers, contended that the germinal vesicle in 



