CHAP. VIII. HYBERNATION OF REPTILES. 239 



We shall now take a rapid view of the animal circle, 

 and slightly touch upon such as afford us examples of 

 these instincts. The first two will be treated of con- 

 jointly ; the migration of animals, separately. 



(253.) Of the manner in which such zoophytes and 

 animalcula; as survive the year, pass the winter months, 

 in cold latitudes, we know very little. The greater 

 part of those which are not formed to survive the year, 

 naturally perish, having reached their destined age ; but 

 such as are of longer life, and are endowed with loco- 

 motion, in all probability retire to the deep recesses of 

 the ocean, or, at least, beyond the influence of atmo- 

 spheric air ; while, according to Ellis *, they are gene- 

 rally found to be contracted, or torpid, during this 

 period. With regard to the Mollusca, or shellfish, 

 our information is equally defective. From the num- 

 ber of empty shells frequently seen on the margins of 

 our freshwater ponds, it seems probable that several of 

 our native fluviatile univalves perish in autumn, while 

 the rest retire to the deepest crevices. Most of the 

 land shells close the opening of their habitations, at the 

 beginning of winter, with a thick white cover, or false 

 operculum t, by which it is securely sheltered ; they 

 also seek a further protection in the hollows of banks 

 and trees. The garden slug generally forms for itself 

 a winter retreat beneath the earth, close to the roots of 

 plants. 



(254.) REPTILES are particularly subject to the law 

 of torpidity. The Greek tortoise ( Testudo Grteca), and 

 probably others of the same group, burrows a hole in the 

 ground, into which it retires for several months. White 

 of Selborne, who attentively observed the manners and 

 habits of one of these animals, states, that it regularly 

 took up its subterranean station in November, and did 

 not reappear until the following April. Having oc- 

 casion to carry it from the residence of the lady to 

 whom it belonged, to his own house in Hampshire, it 



* Essay on Coral. Introd. p. 14. 



t The true operculum of spiral shells is always either horny and elastic, 

 or stony and rigid. 



