GENERAL ZOOLOGY 



VERTEBRATE. An animal possessing a vertebral column. CJ. INVERTEBRATE. 



VESICLE. Any small, sac-like structure. 



VESSEL. A tube, or canal, by which a fluid is conducted; usually restricted to 



those carrying blood and lymph. CJ. DUCT. 

 VESTIGIAL. Any organ at a given stage of development that is less developed in 



one individual than in another is vestigial in the former; having been better 



developed at an earlier stage of development or in a lower organism. CJ. 



RUDIMENTARY. 

 VILLUS {pi. VILLI). A minute, finger-like projection, containing blood vessels and 



occurring in great numbers, as in the intestine of vertebrates. CJ. TYPHLOSOLE. 

 VISCERA {sing. VISCUS). The internal organs of the body; specifically, the organs 



surrounded by the coelom. 

 VISUAL. Pertaining to sight. 

 VITAMINS. A group of organic compounds, occurring in small quantities in certain 



foods and necessary for normal metabolism. 

 VIVIPAROUS. Giving birth to young that develop from eggs within the body of the 



mother and are nourished from the blood stream of the mother. CJ. OVIPAROUS 



and OVOVIVIPAROUS. 



WHITE BLOOD CELL. See LEUCOCYTE and LYMPHOCYTE. 



WORM. In popular language, any small, elongate, creeping animal; specifically, 



such animals as are placed in several different groups, for example, the Platy- 



helminthes, Nematoda, and Annelida. 



X-CHROMOSOME. A sex chromosome that is paired in one sex and single in the 

 other, where it may or may not be associated with a Y-chromosome. 



Y-CHROMOSOME. A sex chromosome that occurs in only one sex, if at all, and is 



not paired; carries very few genes. 

 YOLK. Complex food material stored in a female germ cell or an associated cell 



and used during development. 



ZOOGEOGRAPHY. The science of the distribution of animals over the surface of the 

 earth at a given period of time. CJ. PALEONTOLOGY. 



ZOOID. Any member of a colony of metazoan animals; specifically, one of the in- 

 dividuals of which an ectoproct or coelenterate colony is composed. CJ. POLYP. 



ZOOLOGY. The science of animal life. 



ZYGOTE. A cell produced by the union of two gametes. 



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