6io 



THE INVERTEBRATA 



masses of cells on the funiculus and are enclosed by chitinous shells. 

 The polypides die down during the winter and in the spring the 

 statoblasts germinate and produce new colonies. 



avc- 



Fig. 418, Polymorphism of Polyzoa. After Harmer. A, Bugula. Portion of a 

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

 ten. protruded, ten/ retracted. Crista. B, Portion of colony with ovicell (ovc), 

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

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



Fig. 419. An avicularium of Bugula. Magnified. From Hincks. b. 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. 



The free-swimming larvae may be assigned to the " trochosphere " 

 type. In most cases they are much modified and only the larvae of 

 the Entoprocta and the Cyphonautes larva among the Ectoprocta 

 possess an alimentary canal and are able to feed. The Cyphonautes is, 



