GLOSSARY 241 



Terminal: toward or at the posterior or the distal end. 



Test: the tunic of the ascidian; the rigid shell of the sea urchin. 



Testis: the male sexual gland. 



Thorax: the body division of arthropods following the head ; the chest of 

 vertebrates. 



Tibia: the segment of an insect's leg ; a bone in the shank of vertebrates. 



Tiedemann's vesicles: minute diverticula of the ring canal of the star- 

 fish. 



Trachea: a respiratory tube. 



Trichocyst: a cyst containing a defensive bristle in the ectosarc of Infu- 

 soria. 



Trivium: the three rays of an echinoderm opposite to the bivium. 



Trochanter: the segment of an insect's or a spider's leg, between the coxa 

 and the femur. 



Trochophore: a larval form common to polychaetous annelids. 



Tunic: the outer cuticular covering of tunicates. 



Umbo: the protuberance above the hinge on the shell of a pelecypod. 



Ureter: a tube forming the outlet of the kidney. 



Uropod: the sixth swimmeret of the macruran decapod, that which forms 



the swimming tail. 

 Uterus: a dilated portion of the oviduct in which the egg or the developing 



animal is detained. 



Vagina: the terminal division of the female reproductive tract. 



Vas deferens: a duct leading from the testis toward the external opening, 



the sperm duct. 

 Vegetative organs: those organs which have to do with the processes of 



nutrition, growth, and the expulsion of wastes. 

 Vein: a vessel which brings blood toward the heart. 

 Velum: the circular muscular membrane of a medusa. 

 Ventral: on or toward the underside of an animal. 



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

 Viscera: the organs within the body cavities. 

 Visceral mass: the compact group of organs comprising the principal 



viscera in moUusks. 



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



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

 Zooecium: the outer cuticular covering of a bryozoan. 



