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, 88. 
Zoéa: a larval form of the crab and of certain other crustaceans, 51. 
Zocecium: the outer cuticular covering of a bryozoan, 85. 
