Variation, 466 ; in stature, 63 ; normal, 68 



Vegetables, 125 



Vegetative propagation, vS62, 372 



Veins, of body, 189 



Venation of leaves, 43 



Venom, 233 



Ventral root, 279 



Ventricle, 190, 191 



Vermiform appendix, 174, 175 



Vertebrates, 45, 695 ; plan of, 48 ; limbs of, 

 49; bones and teeth of, 100; metamor- 

 phosis in, 355; reproduction in, 377 f.; 

 aquatic, 378 ; stages of, 459 



Vestigial (ves tij'i d\) structures, 460 



ViUi (vil'i), 170, 171 



Vinci, Leonardo da (1452-1519), 452 



Virginia creeper, 12 



Viruses (vi'r»s ez), frontispiece; of infantile 

 paralysis, 294, 444; disease from, 614 



Vitalism, 441, 443 



Vitamin chart, 132 f. 



Vitamin A, 125, 132 



Vitamin Bi, 104, 128, 132 



Vitamin B2, 108 



Vitamin C, 108, 132 



Vitamin D, 108, 125, 132 



Vitamin G, 108, 128, 132 



Vitamin K, 108, 132 



Vitamins (vi'tfl minz), discovery of, 104 flf., 

 132 f. ; action of, 107 ff. ; naming of, 

 108; differentiating, 108 f.; sources of, 

 109 f. 



Viviparous (v! vip'fl riis) species, 378, 422 



Vocal cords, 62 



Vol vox, 419 



Vries, Hugo de (1848-1935), 479, 510 



Walking, significance of, 46 

 WaUace, Alfred R. (1823-1913), 466 

 Walls, of ceUs, 24 

 Walrus, 5 ; teeth of, 177 

 Warm-blooded animals, 116 

 Wartime, food in, 632 

 Wasp, 352 

 Wasserman test, 242 



Wastes, from cells, 214; plant, 215, 216; 



from animals, 216 ff.; removal of, by 



kidneys, 220, 221 

 Water, and life, 78; in protoplasm, 80 ff., 



98 ; adjustments to supply of, 89 ff . ; 



effect of amounts of, 254 ; pollination 



by, 407 

 Water-soluble vitamins, 132 

 Water supply, 630 

 W-chromosome, 492 

 Weapons, of Stone Age, 55 

 Weight, annual gains in, 115; and basal 



metabolism, 121 

 Weismann, August (1834-1914), 507 

 Went, Frits W. (1903- ), 257 

 Whale, 699 ; brain of, 278 

 Wheat, 251 ; breeding of, 497 

 Wheelworms, 693 

 Whooping cough, 235 

 Whorl of fingerprint, 73 

 Widal's test, 241, 242 

 Wilting, 87, 88 



Wind, pollination by, 407, 408 

 Wings, comparison of, 18 

 Wood, composition of, 84 

 Woodchuck, 177 

 Workers, energy needs of, 123 

 Worms, tube, 92 ; parasitic, 614 f. 

 Wounds, 617 f. 



X rays, pictures by, 189; and mutations, 



512 f. 

 X-chromosome, 492 

 Xenon, 84 

 Xylem (zl'lem), 144, 145, 147 



Yak, 7 



Y-chromosome, 492 

 Yeast, 24, 370, 371,689 

 Yellow fever, 235, 445; and mosquitoes, 

 621 ff. 



Z-chromosome, 492 

 Zygospore (zl'gospSr), 375 

 Zygote, 375 



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