EYES OF GASTEKOPODS. 



295 



functions, which an enlightened research is continually finding 

 in creation. 



Compound stomach of Sea-Hare. 



Though not so gifted as the cephalopods, many of the gastero- 

 pods possess all the organs of sense. Like them, they have an 

 apparatus specially calculated to appreciate sonorous undula- 

 tions, and consisting of a membranous vesicle attached to an 

 auditive nerve, and containing either a single spherical otolithe 

 or a larger number of similar smaller calcareous bodies, which 

 by their vibrations communicate the impression of sound to the 

 nerve. Their minute eyes are short-sighted, it is true, and 

 frequently either entirely wanting or, as in the Nudibranchiates, 

 scarcely able to distinguish light from darkness ; but then- 

 inactive habits require no wide field of vision, and thus they 

 see as much of the external world as is necessary for their 



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