SENSE-ORGANS OP CHITON. 



145 



been discovered by Moseley,* they are even more 

 numerous. Chiton itself, indeed, has none; but in 

 Schizochiton there are 300, and in Corephiura more 



Fig. 9R. Schematic representation of the soft and some of the hard parts in a shell of 

 a Chiton ( Acanthopleura), as seen in a section vertical to the surface, and with the 

 margin of the shell lying in the direction of the left side of the drawing, a, 

 Conical termination of sense-organ ; b, b', ends of nerve ; c, nerve ; f, calcareous 

 cornea ; g, lens ; h. iris ; fc. pigmented capsule of eye ; m, body of sense-organ cut 

 across \ n, nerve of eye ; p, nerve of sense-organ ; r, rods of retina. 



than ten thousand. As in Onchidium, they probably 

 arose as modifications of the organs of touch, and are 

 supplied by the same nerves. They possess (1) a 

 cornea, (2) a perfectly transparent and strongly biconvex 

 lens, and (3) the retina, which presents a layer of sliort 

 but well-deiined rods. It is interesting that they point 

 towards the light, and not, as in Onchidium, away 

 from it. 



* " On the Presence of Eyes in Sheila ot certain Chitonidse," 

 Quarterly Journal of Microscopal Science, 1885. 



