NERVOUS SYSTEM AND SENSE-ORGANS 



That the otocysts are concerned with equilibrium and adjustment 

 of movement has been definitely proved by experiments upon the 

 Prawn (Paltzmon). When this creature moults it sheds not 

 only the defensive armour of the body but also the lining of 



the otocysts, getting rid at the 

 same time of the sand grains 

 which serve as otoliths. Under 

 ordinary ^ circumstances these 

 would be replaced by a fresh 

 supply of the same material, but 

 the specimens experimented upon 



Fig. 1045. Otocyst of Lobster (A) in longitudinal sec- . i i 1 



tion, enlarged and diagrammatic; sensory bristles are seen WCrC Only prOVlded With iron 



projecting into its cavity, which contains numerous oto- c.\* / 1 1 i 



liths;J\fe. f nerve. B, A sensory bristle, further enlarged tllingS, SOttlC Of which in due 



course were introduced into the 



otocysts. It was then found possible by means of a magnet to 

 move the particles in various ways, and as a result of this the 

 Prawns could be induced to assume all sorts of positions, under 

 the impression, so to speak, that they were falling over in this 

 or that direction, which they would have been if the shifting of 

 the otoliths had been produced by ordinary causes. 



ANTE 



THORACIC 



LIMBS 

 Fig. 1046. Opossum Shrimp (Mysis), enlarged. One of the otocysts (EAR) is seen in the tail 



In one Crustacean, the Opossum Shrimp (Mysis), the otocysts. 

 in this case closed, are lodged in the flaps of the tail-fin, but why 

 they should have this position is not known (fig. 1046). 



It is generally assumed that animals which are endowed with 

 a voice or its equivalent also possess powers of hearing, at least 

 if the voice is used for the benefit of one another. Since some 



