ORGANIC RESPONSE 289 



found that these swim about until they encounter a 

 crab, to which they attach themselves at the root 

 of a hair. The little larva then forces an entrance 

 into the body of its host and begins to grow, as a 

 plant forces its roots into the ground. At the same 



FIG. 104. Sacculina attached to the abdomen of a crab: ks, the 

 sac-like parasite giving off root-like processes that permeate the body of 

 the host. (From Lang, after Delage.) 



time it casts off bodily the abdomen with its attached 

 appendages, and its larval sense-organs, including 

 those of sight, begin to retrogress and soon disap- 

 pear. There is no need for digestive organs, as the 



