Fig. i 



Fig. 2 Fig. 3 



Fig. 1 — A lamprey. (After Goode.) 



Fig. 2 — Sacculina; A, parasite attached to a crab; B, the active larval con 

 dition; C, the adult removed from its host. (After Haeckel.) 



Fig. 3 — Trichina spiralis encysted in muscle of a pig. (From Kellogg' 

 Elementary Zool.) 



