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 Cyprida are found in stagnant water, living on dead 
animal matter and confervae. 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 ; 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 Gypridcz are 
very lively and active. 
