OB BATS. 73 



are apprised of the proximity of objects, probably 

 in consequence of a difference in the impulse given 

 by the air; insomuch that a Bat, if deprived of 

 its eyes, can find 'its way on wing, without com- 

 ing into contact with cords or other impediments 

 purposely arranged in a room. On the ground, 

 the motions of these animals are exceedingly con- 

 strained. They are all nocturnal or crepuscular, 

 roaming about in the dusk, or in cloudy weather, 

 and reposing by day in caverns, crevices, and other 

 concealed places, where they fasten themselves by 

 their hind feet, hanging with their head downwards. 

 But when resting for a short time, or climbing, they 

 employ the hooked claws of the first toe of their 

 fore feet. In cold climates, Bats undergo a partial 

 torpidity, retiring for that purpose to holes or cre- 

 vices in buildings, caves, or trees; but a moderate 

 increase of temperature serves to arouse them, so 

 that with us, they are sometimes seen abroad on a 

 fine evening in the end of November or the be- 

 ginning of February, and when discovered in 

 their retreats in the midst of winter, they exhibit 

 sensibility, or even emit a faint cry on being 

 seized. 



Without entering into a historical relation of the 

 progress of discovery with regard to these animals, 

 it will suffice here to refer the reader to Mr Gray's 

 " Revision of the Genera of Bats," in the 12th num- 

 ber of the Magazine of Zoology and Botany, where 

 he will find a succinct account of it. Mr Gray 

 defines the Family of VESPERTILIONID.E as follows : 



