336 



FISHES. 



[Chap. 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 Ampullaria 

 and Planorbes, as well as the Palu- 

 dino 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. Princif. of 

 Geology, Sfc. p. 373. 



1 Hunter's Observations on farts 

 of the Animal (Economy, p. 88. 



2 Centetes ecaudatus, Illiger. 



