COMMON FROG. 97 
during its passage. When first expelled it consists of nu- 
merous small opake globular bodies, enveloped in a small 
glairy, or glutinous mass. This latter substance soon ab- 
sorbs a large quantity of water, and, in the course of an 
hour or two, each becomes not less than a quarter of an 
inch in diameter. The consequence of this augmentation 
in the bulk of the transparent mass, surrounding each em- 
bryo, is, that all the latter are removed from each other by 
a whole diameter of each globe ; and they appear like black 
dots regularly distributed throughout a large mass of trans- 
parent jelly. 
The deposit of the eggs takes place at the bottom of the 
water, notwithstanding the assertion of some naturalists, 
and of Résel amongst them, that they are expelled at the 
surface. The mistake, probably, arose from the mass of 
eggs being generally found at the surface; but this arises 
merely from the disengagement of gas in the substance of 
the glairy envelope, in consequence of partial decompo- 
sition. 
The changes which now begin to take place in the em- 
bryo are most interesting. They have been detailed in a 
very minute and satisfactory manner by Rusconi in his 
work, already alluded to; and I have taken considerable 
pains during the last spring to follow out his investigations, 
and by actual observation to correct or confirm his account. 
I may here observe, once for all, that, with the exception 
of a few of the details in the earliest periods, I have been 
able to satisfy myself of his correctness; and in those 
points, I believe that I only failed to do so, partly by my 
not having obtained the ova immediately after their expul- 
sion, and partly by the want of time to enter into all the 
necessary minutie of the investigation. 
Ihave also to observe that the developement of the young 
H 
