424 BIOLOGY 



veins. Blood vessels carrying blood to the heart, 190; the fibro vascular 



bundles in a leaf, 114. 

 vent. See anus. 

 ventral side, 155. 

 ventral cord. The nerve cord on the ventral side of the body cavity of 



the earthworm and some other animals, 163, 171. 

 ventricle (Lat. venter = stomach). The lower chamber of the heart that 



forces blood into the arteries, 188. 

 venus sinus. A large blood vessel on the dorsal side of the heart of a frog 



into which the venus blood collects before passing into the right auricle, 



188. 



vertebrae. The separate bones of the backbone or spinal column, 177. 

 Vertebrata. Animals which possess a backbone or its equivalent, 176, 



373. 



vesicle. A sac. 



vessel (Lat. vasa = a vessel). Any hollow tube or cavity, 105. 

 vestigial organs. Functionless remains of organs, formerly larger and 



functional, 

 villi. Projections on the inside of the intestine which serve to absorb 



food, 308. 

 viola, 372. 



viscera. The organs of the abdominal cavity, 175. 

 vital energy, or vitality, 41, 309, 319. 



vitalistic theories. The theories that regard life as a distinct force, 323. 

 vitelline membrane (Lat. vitellus = yolk). A cell wall of an ovum, 249. 

 vitreous humor (Lat. vitrum = glass). The transparent liquid back of 



the lens and filling the eyeball, 197. 

 viviparous. Producing young alive, 290. 

 vocal cords. The membranes in the larynx whose vibration produces the 



voice, 209. 

 vomers, 180. 

 VON MOHL, 40. 

 Vorticella, 91. 



warm-blooded. With blood that always maintains an equable tempera- 

 ture. 



WEISMANN, 328, 355. 

 wilts, 232. 

 winter eggs. Eggs of certain animals, designed to live over winter, usually 



requiring fertilization, in distinction from summer eggs which do not, 



247. 



Wolffian body. The primitive kidney found in the vertebrate embryo, 

 wood. Same as xylem. 



