CRUSTACEAXS 



53 



conclude as to the alertness of their senses ? Does the cov- 

 ering of their bodies suggest the possession of a delicate or 

 a dull sense of touch? 



Of what motions are the eyes capable ? Touch one of 

 the eyes. The result? Can a crayfish see in all direc- 

 tions? To test this, place a crayfish on a table and try 

 whether you can move to a place where you can see the 



Fig. 8i. — Crawfish 

 (dorsal surface). 



Fig. 82. 



crayfish without seeing its eyes. What are the advantages 

 and disadvantages of having the eyes on stalks ? 



Touch the body and the several appendages of the 

 crayfish. Where does it seem most sensitive to touch ? 

 Which can reach farther, the antennae or the big claws? 

 Why are short feelers needed as well as long ones ? 



Make a loud and sudden noise without jarring the cray- 

 fish. Is it affected by sound? 



External Anatomy (Figs. 81, 82, 83, 84). — Is the body of 

 the crayfish rounded out (convex) everywhere, or is any 

 part of its surface either flat or rounded in (concave) ? 



