GLOSSARY 223 



Ventral : on or towards the underside of an animal. 



Ventricle : a chamber of the heart from which blood is sent over the body ; 



mussel, 94 ; clam, 108 ; oyster, 101 ; snail, 115. 

 Vesicula seminalis : a sperm-sac in the male animal ; squid, 132. 

 Viscera : the organs within the body -cavities-. 

 Visceral mass : the compact group of organs comprising the principal viscera 



in mollusks; mussel, 90; oyster, 100; clam, 104; snail, 113; squid, 125. 



Wing-covers : the first pair of wings of a beetle, the elytra, 5. 



Yolk glands : planarian, 77 ; tapeworm, 83. 



Zoea : a larval form of the crab and of certain other crustaceans, 51. 

 Zocecium : the outer cuticular covering of a bryozoan, 85. 



