ANIMAL PARASITES 



295 



to the crab b}' means of the feeding rootlets. Loss by 

 degeneration of the body-parts is carried very far in this 

 case. 



Internal parasites. — Inside the body of most animals 

 live various parasites belonging to the great branch of 



F'iG. 231. — Saccnlina, a parasitic crustacean; A, attached to a crab, the 

 root-like processes of the parasite penetrating the body of the host ; j5, 

 the active larval condition; C, the adult removed from its host. 

 (After Haeckel.) 



worms. The tapeworm and the deadly trichina (see 

 p. 146) are conspicuous examples of these. The tape- 

 worm (fig. 233) has the form of a narrow ribbon, perhaps 

 several yards long, attached at one end to the wall of 

 the intestine, while the remainder hangs freely in the 



