282 HISTORY OF BRITISH CRUSTACEA. 



brittle, and seems to be endued externally with a species of 

 varnish, to protect them from the action of the water ; as 

 whenever they rise to the surface, the shell becomes per- 

 fectly dry, and floats there in spite of the animal's struggles 

 again to immerse itself." 



The Cj/prida are found in stagnant water, living on dead 

 animal matter and conferva?. They deposit spherical eggs 

 upon plants, fixing themselves when so engaged so firmly 

 that no agitation of the water displaces them ; the eggs are 

 hatched in a few days. Before they acquire the adult state, 

 they undergo several moultings. Dr. Baird says, "The re- 

 newing of the shell forms a fine example of the process of 

 exuviation j the change which takes place being most com- 

 plete, for not only does the shell itself fall off, but the ani- 

 mal even casts off the internal parts of the body, the fine 

 pectiniform branchiae, and the minutest hairs clothing the 

 setae of the antennae," etc. He informs us that when the 

 ponds in which they live dry up in summer, they bury 

 themselves in the mud, and are thus often preserved in the 

 moisture until the fall of rain again fills their habitations. 

 The eggs, even when the mud in which they are placed is 

 dry and hard, do not lose their vitality. The Cj/prida are 

 very lively and active. 



