INDEX 



649 



Wireworms, 290 



Wolf spider, 306 



Wolff, Caspar, 583 



Wolves, 426, 436, 535 



Woodchuck, 445 



Woodpeckers, 413, 418, 509, 537 



beak, 412 



young, 418 

 Woodruff, L. L., 76 

 Worker ants, 299 

 Worker bees, 296, 297 

 Worm lizards, 390 

 Worms, 477, 494, 522, 525 



(See also various types by name) 

 Wrigglers, 293 

 Wuchereria bancrofti, 184 



X-body, 475 



X-chromosomes, 566, 568-569 

 X-rays, 549, 562 



Y-chromosomes, 566, 567-568 

 Yellow marrow, 326 



Yellowlegs, beak, 412 



foot, 413 

 Yellowthroat, 509 



foot, 413 

 Yerkes, 377 

 Yolk, 111, 112, 118-121, 164, 173. 383 



cells, 164, 173 



circulation, 385 



ducts, 168, 169 



glands, 162, 163, 168, 170, 173, 189 



plug, 378 



sac, 361, 384, 444, 446 



stalk, 384, 446 



Z 



Zebra, 534 



Zinc, 20 



Zoaea, 270, 271 



Zona pellucida, 444 



Zooecium, 190, 191 



Zoogeographical regions, 632, 633 



Zoogeography, 5, 510, 527-537 



Zoology (general), 3-6, 41 



Zoophytes, 145 



Zygote, 46, 87, 89, 96, 475, 556, 566-568 



Zymogen, 99, 100, 492 



