INDEX 



585 



Viscera, of vertebrates, 47, 49. 



Vitamins, 77, 79. 



Viviparous development, 421. 



Vocal cords, 21. 



Volvocina, 197. 



Volvox, 199, 200, 215, 216 243. 



Vorticella, 190. 



de Vries, Mutation Theory of, 558. 



Walking sticks, 373. 



Wallace, 546; Natural Selection 



chart of, 546. 

 Warrior grasshopper, 348. 

 Wasps, 375, 388; social, 390; s:)li- 



tary, 388, 389. 

 Water flea, 255, 333, 334. 

 Weismann, 224. 

 Wiedersheim, 532. 

 Wilson, 471, 474. 



Wings, of locust, 347; of vertebrates, 



501. 

 Wolves, 31. 

 Wood frog, 12, 16. 

 Woodruff, 184. 



X-chromosome, see Sex-chromosome. 



Y-chromosome, see Sex-chromosome. 

 Yolk, 135; of bird egg, 427. 

 Y'olk-sac, 422, 431. 

 Yolk-stalk, 422, 431. 



Zoochlorellae, 259. 

 Zodgeography, 3, 5, 6, 507, 519. 

 Zoological sciences, 2, 3, 4, 5, 6. 

 Zoomastigina, 1.55, 174. 

 Zoothamnium, 190. 

 Zygote, 174, 187, 214, 218, 403. 



