198 ASSOCIATION OF ORGANISMS—THE WEB OF LIFE 
Fig. 1146.—Sacculina. a, Shore-Crab (Cavcinus menas), with the parasite projecting from the under side 
of its tail. B-G, Stages in development, greatly enlarged; B, nauplius stage, with two pairs of feelers (1, 2) and 
one pair of jaws (3); c, mussel-shrimp stage, showing modified first pair of feelers (/); D, the same, attached 
by one feeler (/) to the base of a crab’s bristle (47.), the hinder part of body is being thrown off; E, F, G, later 
stages, showing formation of a tube (¢) through which the soft substance of the parasite passes into the crab. 
