206 GLOSSARY. 



Vitellarium. A female reproductive gland that supplies cells to be used 



as food for developing embryos. See Bdelloura. 

 Vitelline glands. Same as vitellarium. 



Water tube. One of the tubes between the lamellae of a lamellibranch 



gill. 

 Whorl. A turn of the shell of a gastropod. 



Yolk -mass. A mass of food material for the nourishment of an embryo. 



Zoophyte. An animal that is somewhat plant-like in appearance. 

 Zooid. One of the individuals in a united colony of animals. See Obelia 

 and Bugula. 



