534 



THE INVERTEBRATA 



tasks which in the Hydrozoa are allotted to the dactylozooids and in 

 the Echinodermata to the pedicellariae. 



Many of the Polyzoa have free-swimming larvae which may be 



avc. 



Fig. 393. Polymorphism of Polyzoa. After Harmer, A,Bugula. Portion of a 

 colony, avc. avicularium; ovc. ovicell; tentacles of ordinary individuals, 

 ten. protruded, ten.' retracted. Crisia. B, Portion of colony with ovicell {ovc.), 

 surface view. B', Section through ovicell to show emb.' primary embryo; 

 emb." secondary embryos ;/o/. follicular tissue. 



Pig- 394- An avicularium of Bugula. Magnified. From Hincks. h. beak; 

 C. chamber representing the body cavity of the modified individual; dm. 

 muscle which opens, om. muscle which closes the mandible on the beak; 

 md. mandible, the operculum of the modified cell; p. stalk. 



assigned to the " trochosphere " type. In most cases they are much 

 modified and only the larvae of the Entoprocta and the Cvphonautes 

 larva among the Ectoprocta possess an alimentary canal and are able 



