304 THE WORLD OF THE SEA. 
Crustaceans have separate sexes, the males not differing greatly 
from the females. This, however, is not universally the case, for 
there are crustaceans which exist as parasites on certain fish— 
among which the male is much smaller than the female—and here 
the order of governance must be reversed, the women must be the 
directors of the men, for they accommodate their husbands with a 
lodging in a groove in their backs. The false claws (as we may 
term the short appendages in the drawing we give) are employed 
by the female for holding her eggs, which she carries about with 
her. A shrimp has been known to have 6,807 eggs; a crab, 
21,699; other species are still more prolific, producing even as 
many as 100,000 at once: three or four such crustaceans would be 
THE LARVA OF A COMMON CRAB, 
sufficient in six months to engender a crustacean nation equal 
to the population of Portugal. The crustacean eggs are generally 
red or yellow, and small. They have a property, which although 
peculiar, is shared by the eggs of many other species: that is, 
they may be preserved dry for a considerable time, and yet retain 
their vitality, and under favourable circumstances produce young 
crustaceans. When the eggs are hatched, they become more 
transparent and larger; the membrane which encloses being thin 
and transparent, the eyes of the yellow embryo can be plainly seen 
within it. 
The yellow, or the yolk, does not communicate with the belly 
of the embryo, as is the case in the embryo of a fowl, but with the 
