240 Royal Society :— 
ova enlarged as usual, but did not arrive satisfactorily through the 
branchial state; most of the ova appeared to undergo no change 
whatever. 
Experiment 3rd.—Some spawn was placed 8 inches below the 
surface of the water ; but none of the ova passed through the branchial 
state. 
Experiment 4th.—A quantity of spawn was placed on rock work 
near the surface of the water. Nearly all the ova passed satisfac- 
torily through the branchial state to the formation of tadpoles ; each 
of the experiments was made at the same time and at the same tem- 
perature. 
Experiment 5th.—A quantity of spawn was put into two round 
shallow dishes, each containing two pints of water, which were placed 
on the stand of the aquarium at the same time as in the former experi- 
ments; nearly all did well; and during the full branchial or fish-like 
state, great numbers of the embryos had placed themselves close to 
the margin of the water, forming a dark circle, with their branchize 
nearly exposed to the atmospheric air. They do not appear to feed 
during this period on the jelly—their first food ; atmospheric respira- 
tion seems more needful than food for their existence for several 
days during their full branchial state*. 
There are two distinct metamorphoses from the ovum to the full 
development of the frog: the first from the branchial or fish-like state 
to that of the tadpole; the second from the tadpole to that of a frog, 
—the first requiring for its existence a close approximation to the at- 
mospheric air, the second requiring full atmospheric respiration, to 
which I shall hereafter refer. 
The branchial state continues about nine days, from the first bud- 
dings of the branchize to their absorption. About the seventh day 
the branchiz are absorbed on the right side, indeed so quickly that 
I have observed that scores have lost them during one night, whilst 
the branchize on the left side have apparently been perfect ; but these 
in their turn become absorbed during the next day ; the respiration 
of this newly formed tadpole now depends on the internal gills and 
cutaneous surface. The gill-opening for the passage of water is 
very apparent on the left side, but there is none on the right. 
2. On the Influence of Light on the Tadpole. 
The experiments of Dr. Edwards indicate that a decided influence 
is exerted by light upon the metamorphosis of Batrachians, since, 
according to his statement, when tadpoles which had arrived at 
nearly their full growth were secluded from the influence of light, 
* The ova of the toad appear to be less tenacious of life than those of the frog. 
I have observed, when they are placed 4 or 5 inches below the surface of the water, 
they all die; but they live when the long jelly lines in which the ova are enclosed 
are floated on weeds, or on a network of sticks on the surface of the water. In 
my note-book on the tadpole of the toad in 1849, 1 found that after the gelatinous 
lines began to break up on the surface of the water, and the ova to separate from 
them, a number of the eggs undergoing the metamorphosis adhered to the sticks 
and weed, but those falling to the bottom of the vessel perished. 
