336 
FISHES. 
[CHAif. X. 
Dr. John Hunter 1 has advanced an opinion that hy- 
bernation, although a result of cold, is not its immediate 
consequence, but is attributable to that deprivation of 
food and other essentials which extreme cold occasions, 
and against the recurrence of which nature makes a 
timely provision by a suspension of her functions. Ex-> 
cessive heat in the tropics produces an effect upon ani-^ 
mals and vegetables analogous to that of excessive cold 
in northern regions, and hence it is reasonable to suppose 
that the torpor induced by the one may be but the coun- 
terpart of the hybernation which results from the other. 
The frost that imprisons the alligator in the Mississippi 
as effectually cuts it off from food and action as the 
drought which incarcerates the crocodile in the sun-burnt 
clay of a Ceylon tank. The hedgehog of Europe enters 
on a period of absolute torpidity as soon as the incle- 
mency of winter deprives it of its ordinary supply of 
slugs and insects ; and the tenrec 2 of Madagascar, its 
tropical representative, exhibits the same tendency 
during the period when excessive heat produces in that 
climate a like result. 
the ground, "pushing aside the 
moistened earth and coming forth 
from their retreats; "but on the 
disappearance of the water not one 
of them was to be seen above 
ground. Wishing to ascertain what 
had become of them he turned up 
the earth at the base of several 
trees, and invariably found the 
shells buried from an inch to two 
inches below the surface." Lieut. 
Hutton adds that the Ampullarice 
and Planorbes, as well as the Palu- 
dince are found in similar situa- 
tions during the heats of the dry 
season. The British Pisidea ex- 
hibit the same faculty (see a mo- 
nograph in the Camb. Phil. Trans. 
vol. iv.). The fact is elsewhere 
alluded to in the present work of 
the power possessed by the land 
leech of Ceylon of retaining vitality 
even after being parched to hard- 
ness during the heat of the rainless 
season. Lyell mentions the in- 
stance of some snails in Italy which, 
when they hybernate, descend to 
the depth of five feet and more 
below the surface. Princip. of 
Geology, %c. p. 373. 
1 Hunter's Observations on parts 
of the Animal (Economy, p. 88. 
2 Centetes ecaudatus, ILLiger. 
