308 THE WORLD OF THE SEA. 
cannot wonder that former naturalists considered the young 
craw-fish belonged to quite a distinct genus, which they termed 
Phyllosoma. 
LARVA OF THE CRAW-FISH. 
The larvae have one peculiarity in common with their parents, 
that is, they moult; they change their carapace four times in the 
forty days of their roving life. Each time the carapace is replaced 
YOUNG LOBSTERS SIX TIMES THEIR NATURAL SIZE. , 
(Az the period of thetr third moult.) 
it is thicker, and as the tail is their chief oar, at last it becomes 
so stiff as not to be able to make its swimming movements rapidly 
enough, and so the larva sinks to the bottom. 
