Nhvous System aftd Senses. HS"^ 



plain this and similar facts only on the supposition of the 

 existence of a sense of touch feelingly alive to impressions 

 impalpable to our grosser sense. 



Molluscous animals are dumb, one only (Tritonia arbores- 



cens {^g. 108.) 

 having been ob- 

 served to pro- 

 duce a sound of 

 any kind. The 

 sounds this Tri- 

 t6ni« produces, 

 10^ W when in a glass 



vessel, says Professor Grant, " resemble very much the 

 clink of a steel wire on the side of the jar, one stroke only 

 being given at a time, and repeated at intervals of a minute 

 or two : when placed in a large basin of water, the sound is 

 much obscured, and is like that of a watch, one stroke being 

 repeated as before at intervals. The sound is longest and 

 oftenest repeated when the Trit6ni<:^ are lively and moving 

 about, and is not heard when they are cold and without any 

 motion ; in the dark I have not observed any light emitted 

 at the time of the stroke; no globule of air escapes to the 

 surface of the water, nor is any ripple produced on the sur- 

 face at the instant of the stroke; the sound, when in a glass 

 vessel, is mellow and distinct." The Professor has kept 

 these Trit6ni<^ alive in his room for a month, and, during the 

 whole period of their confinement, they have continued to 

 produce the sounds, with very little diminution of their ori- 

 ginal intensity. In a still apartment they are audible at the 

 distance of twelve feet. "The sounds obviously proceed 

 from the mouth of the animal ; and at the instant of the 

 stroke we observe the lips suddenly separate, as if to allow 

 the water to rush into a small vacuum formed within. As 

 these animals are hermaphrodites, requiring mutual impreg- 

 nation, the sounds may possibly be a means of communica- 

 tion between them ; or, if they be of an electric nature, they 

 may be a means of defending from foreign enemies one of 

 the most delicate, defenceless, and beautiful gasteropodes 

 that inhabit the deep." {Edin, Phil. Journ., vol. xiv. p. 186.) 



I am. Sir, yours, &c. 

 March 31. 1831. G. J. 



