INDEX 



Visual cells, of vertebrates, 107 



V^isual purple, see Rhodopsin 



Visual sensitivity of insects, 451 



Vitamin A, 31, 76, 107 



Vitamin B,, see Thiamine 



Vitamin B.,, see Riboflavin 



Vitamin B,;, see Pyridoxine 



Vitamin B,^, see Cyanocobalamin 



Vitamin C, see Ascorbic acid 



Vitamin D, 26, 31, 76 



Vitamin E, 31 



Vitamin G, see Riboflavin 



Vitamin H, see Biotin 



Vitamin K, 32, 64, 74, 76 



Vitamins, 29, 30-34, 74, 118; fat soluble, 31, 



76; water soluble, 32 

 Viviparous reproduction, 132; in mammals, 



579 

 Vocal cords, 55 



Voluntary muscles, see Striated muscle 

 Volvocidae, 266-268 

 Volvox, 268, 292; V. aureus, 269; V. globalor, 



268 

 von Frisch, Karl, 475 

 von Mohl, 12 

 I 'oriicelta, 258 

 I'u/tur, 578 



Walking stick, 462 



Walking worm, 483 



Wallalna, 582 



Wallace, Alfred R., 648 



Walrus, 580 



Warble fly, 476 



Warm-blooded animals, 29, 125 



Wasps, 469; social, 470; solitary, 471; tem- 

 perature regulation in, 597 



Waste products, of metabolism, 38, 54, 82, 

 518 



Water, 23, 29, 30, 35, 36, 37, 38, 74, 76, 82, 

 121, 124; and materials in solution, 601; as 

 developmental medium, 602; importance in 

 vital processes, 601; of metabolism, 602; 

 sources of, 602 



Water balance, 103, 118; by protonephridial 

 systems, 519; in aquatic organisms, 601; 

 in protozoans, 518 



Water boatman, 462 



Water loss, 602; and temperature regulation, 

 603 



Water lungs, and excretion, 521; of holo- 

 thurians, 491, 516; of Thyone, 504, 505 



Water relations, of terrestrial animals, 602 

 Water-vascular system, of Anledon, 508; of 



starfish, 494, 495 

 Waxes, see Simple lipids 

 Weevils, 463 



Whale, 580, 589, 61)8, 633 

 White blood cells, 63 

 White fibers, see Collagenous fibers 

 White matter, 96, 101 

 Wiedersheim, 638 

 Wilson, E. B., 182, 185, 209 

 Winter eggs, of rotifers, 347 

 Witschi, Emil, 21 1 

 Wolves, 580 

 Wombat, 579, 609 

 Woodrufl', L. L., 610 

 Worms, segmented, see Annelida; tracks of, 



in stone, 621 

 Wiichereria, 353 



X-chromosome, 42, 136, 190, 209 



X-rays, 207 



Xiphosurida, 216, 423, 481 



Y-chromosome, 42, 136, 190, 209 



Y-organs, 435, 456 



Yellow fever, 476 



Yellow fibers, see Elastic fibers 



Yolk, 20, 139, 146 



Yolk cells, of Clonorchis, 330; of planarians, 



322; of tapeworms, 336 

 Yolk glands, of planarians, 321; of rotifers, 



347 

 Yolk plug, 1 52 

 Yolk sac, 160; of mammals, 589 



^alophw., 586 



Zebra, 580, 588, 625 



Zoaea larva, 440, 442 



Zone of growth, in Nereis, 400, 401; in Poly- 



gordius, 418 

 Zoochlorellac, 286 

 Zooecium, of ectoprocts, 361 

 Zoogeography, 8, 631 

 Zooids, in Ectoprocta, 358, 359; in Rhohdo- 



pleurn, 543 

 Zoology, 8 

 Zoophyta, 223, 286 

 Zoophytes, 486 

 ^oolhammum, 258 

 Zygote, 134, 141, 145, 530; evolutionary 



significance of, 225 



708 



