THE CRUSTACEANS. 305 
back. The larvae do not bear much resemblance to their parents, 
indeed, they often appear in most peculiar forms, as may be judged 
from the drawing we give of the larva of a crab. 
Naturalists used to consider these creatures a separate and 
distinct species. They are all roundish, and have a long projection 
pointing in advance like the beak of the ibis, and another nearer 
the tail like the prick of a gooseberry bush. The body is slender, 
terminating ina tail generally ramified. Its claws are long, and | 
provided with bunches of vibratory cils, by whose aid they can 
swim with great rapidity. As we know, the adult crab is not 
organised for swimming ; this is another instance of that peculiar 
law which constitutes the young of certain creatures upon a dis- 
tinctly different model from their parents. 
U 
