CHIROPTERA 43 



auditory bulla, and a special nasal organ of sense, the " horse- 

 shoe." In all species the whiskers or vibrissse are prominent. 



Although it is difficult to explain the movements of bats by- 

 means of the five human senses, there is no proof of the exist- 

 ence of a sixth. Such a sense, if existing, might be one of 

 direction, and might be located in the inner ear.^ It must be 

 remembered also that different senses may predominate in the 

 various species, for it may be naturally supposed that the acute- 

 ness of each particular sense may vary in relation to the size, food, 

 and general habits of each. In those bats, such as the Noctule 

 and Leisler's, which fly in the subdued daylight of morning and 

 evening rather than in the dark, the power of sight is probably con- 

 siderable, as it may be also in exotic day-flying species. Indeed, 

 the same authority, Mr Whitaker, who showed that in Natterer's 

 Bat the eyes are not necessary for the performance of all normal 

 movements, believes that the Noctule habitually hunts by eye- 

 sight ; and that the Long-eared Bat relies largely on hearing 

 and sight, especially the latter. On the other hand, Mr Bruce 

 F. Cummings finds the sense of sight weak, but that of hearing 

 very acute in the Greater Horseshoe. 



As regards hearing, it is probable that this sense is 

 frequently useful as a means of communication. Its importance 

 to bats is indicated not only by the variable and remarkable 

 development of the ear, but by the great mobility and independ- 

 ence of this organ. It is indeed inconceivable that creatures 

 which, like some bats, are rarely silent should have no percep- 

 tion of the voices of their fellows ; and indeed a young bat calls 

 for its mother as persistently as any other young animal. 

 Most experiments on the hearing of bats are subjected to the 

 difficulty that, the cries of these animals being pitched on a 

 very high scale, their auditory organs are almost certainly 

 attuned accordingly. It is a well-known fact that their ordinary 

 cries, although very perceptible to some human ears, are to 

 others quite inaudible, especially to those of people of mature 

 age. The gamut is, in fact, fixed above that to which human 

 ears are attuned. 



A captive Noctule, when it had become accustomed to its 

 novel surroundings, took no notice of such (to human ears) loud 



1 Hahn, op. cit., 191. 



