EYES OF GASTEROPODS. 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 coramunicate 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 their 
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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