690 



INDEX 



Villus, 71 



Viruses, 400-401 



Vision, 110-112, 472-473 



Visual purple, 59, 111 



Vital properties of protoplasm, 13 



Vitamins, 57-62, 169 



Vitreous humor, 110; 111 



Viviparous reproduction, 228 



W 



Wadjak man, 504, 505 



War, biological effects of, 320 



Warm blood, 457, 661, 662; 594 



Wastes, elimination of, 22, 77-80, 189- 

 190 



Water, absorption of, by roots, 148-150 

 as medium for life, 545-553 

 requirements of human body for, 55, 62 

 transport of, in plants, 146-150, 161- 

 163 



Weismann and evolution, 344 



"White" group of mankind (see Cauca- 

 soids) 



White matter, 107, 118, 120-123; 117 



Wood, 156-157, 159-160; 158 



X 



X, Y chromosomes, 291-292 

 Xylem, 145, 154-160; 1U 



functioning of, 163-165 



primary and secondary, 145, 146 



"Yellow" group of mankind (see Mongo- 

 loids) 

 Yellow spot of eye, 112, 472, 474 

 Yolk, 219-220, 232-233; 236, 238 



and cleavage, 231, 235; 236, 238 

 Yolk sac, 438; 439 



Z 



Zoogeography, 349-351, 379-386 

 of man, 536-538 



Zygote, 222, 231, 283; 220 



in plants, 254, 256, 257, 273; 270 

 in unicellular organisms, 212 



Zygotene, 216; 217 



Zygotic constitution or formula, 283 



