410 PRINCIPLE!^ OF ANIMAL BIOLOGY 



Uterus (u' teru.s). A luodifiod portion of llic oviduct in wliicli Ihc eggs undergo at 

 least part of their development. Strictly the term uterus is applicable only in 

 animals in which the developing eml)ryo becomes attached to the wall of the organ. 



Vacuole (vak'uole). A region within a cell occupied by a liquid other than proto- 

 plasm, usually water with various substances in solution. 



Vagina (va ji' na). The passage leading from the uterus to the exterior in many ani- 

 mals. 



Y a.gus {ra' gus). The tenth cranial nerve. 



Variation {va' ri a' shun) . In biology, the occurrence of differences among the 

 individuals of the same species; also, sometimes, among the individuals or species of 

 larger groups (genera, families, etc.) 



Variety (va ri' e ti). In taxonomy, a division of a species; a group of individuals within 

 a species that differ in some minor respect from the rest of the species. 



Vas deferens {vas' def er enz) {pi., vasa deferentia, vas' a def er en' shi a). A duct 

 conveying sperms from the testis to the exterior. 



Vas efferens {vas' ef fer enz) {pi., vasa efferentia, vas' a efferen'shia). One of a 

 number of minute tubes leading away from a testis, serving to convey the sperma- 

 tozoa. They lead into a larger tube called in many cases the vas deferens. 



Vegetative {vej' etativ). Concerned with nutrition. When applied to an egg, 

 meaning that side near which the yolk is accumulated (vegetative pole). 



Vein {vane). A vessel conveying toward the heart blood which has already traversed 

 capillaries since leaving the heart. 



Velum {ve' lum). A horizontal circular shelf within the margin of a medusa. 



Ventrad {ven' trad). In a ventral direction. 



Ventral {ven' tral) Literally, pertaining to the bcllj-; hence, usuall.v, lower. 



Ventricle {ven' tri k'l) . The posterior chamber of the heart in fishes. Amphibia and some 

 reptiles, and one of the two posterior chambers in higher vertebrates. Its function 

 is the propulsion of the blood through the main arteries and connecting vessels. 



Vertebrata (ver' febra' (a). A subphylum of the phylum Chordata, comprising 

 the backboned animals. For definition see Chapter XII. 



Vertebrate {ver' te hrate). adj. Possessing a backbone, n. An animal having a 



backbone. 

 Vesalius {vesa'lius). A Belgian anatomist and court physician who lived 1514- 



1564. 

 Vibracularia {vi hrak' u la' ri a). Individuals of a Bryozoan colony, in the form of a 



thread. 

 Vlcq d'Azyr, Felix {veek' da zeer') . French comparative anatomist and physiologist, 



1748-1794. 

 Vicuna {ve koon' ya). A llama-like animal of South America. 

 Virchow, Rudolf {veer' ho). A German physiologist and pathologist, 1821-1902. 



Visceral (via' ser al) . Pertaining to the viscera, or organs contained in some large 

 cavity of the body; applied in the vertebrates chiefly to the organs of the abdomen, 

 in clams to the digestive organs and glands above the foot. 



Visual (tdz' ii al) . Pertaining to the sense of sight. 



Vitamine {vi' ta min). One of several substances common in leafy vegetables, 

 animal fats, and (elsewhere, which are necessary for proper metabolism in animals. 

 Their chemical nature is unknown. 



