230 
natural history. 
liquor in •whicli it is circumfused, serves it for nourishment. 
In two days more, some of these little creatures fall to the 
bottom; while others remain swimming in the fluid round 
them, while their vivacity and motion seem to increase. Those 
which fall to the bottom remain there the whole day ; but 
having lengthened themselves a little, for hitherto they are 
doubled up, they mount at intervals, to the mucus, which 
they had quitted, and are seen to feed upon it with great 
vivacity. The next day they acquire their tadpole form. In 
three days more they are perceived to have two little fringes, 
that serve as fins beneath the head ; and these in four daysafter 
assume a more perfect form. It is then also that they are seen 
to feed very greedily upon the pond-weed. When ninety-two 
days old, two small feet are seen beginning to shew near 
the tail; and the head appears to be separate from the body. 
In five days after this, they refuse all vegetable food ; their 
mouth appears furnished with teeth ; and their hinder legs 
are completely formed. In this state it continues for about 
six or eight hours; and then the tail dropping off by de- 
grees, the animal appears in its most perfect form. 
Thus the frog, in less than a day, having changed its figure, 
is seen to change its appetites also. As soon as the animal 
acquires its perfect state, from having fed upon vegetable it 
becomes carnivorous, and lives entirely upon worms and in- 
sects. But, as the water cannot supply these, it is obliged 
to quit its native element, and seek for food upon land, where 
it lives by hunting worms and taking insects by surprise. 
The frog lives for the most part out of the water; but when 
the cold nights begin to set in, it returns to its native ele- 
ment, always choosing stagnant waters, where it can lie with- 
out danger, concealed at the bottom. In this manner it 
continues torpid, or with but very little motion, all the 
winter ; like the rest of the dormant race, it requires no 
food : and the circulation is slowly carried on without any 
assistance from the air. 
The difference of sexes, which was mentioned above, is 
not perceivable in these animals, until they have arrived at 
their fourth year; nor do they begin to propagate, till they 
have completed that period. By comparing their slow 
growth with their other habitudes, it would appear, that 
they live about twelve years; but having so many enemies, 
both by land and water, it is probable that few of them 
arrive at the end of their term. 
Frogslive upon insects of all kinds; butthey never eat any, 
unless they have motion. They continue fixed and immove- 
able till their prey appears; and just when it comes suffi- 
