58 EVENINGS AT THE MICROSCOPE. 



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 surface at the instant of the stroke ; the 

 sound, when in a glass vessel, is mellow and distinct." 

 The Professor has kept these Tritonire 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 original intensity. 

 In a small 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 

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

 these animals are hermaphrodites, requiring mutual 

 impregnation, the sounds may possibly be a means of 

 communication between them ; or, if they are of an 

 electric nature, they may be the means of defending 

 from foreign enemies one of the most delicate, defence- 

 less, and beautiful Gasteropods that inhabit the deep." * 



* "Edinb. Phil. Journ.," xiv. 18G. 



