440 



INDEX 



Ungulata, classified, 271 



Ungulates, 353; absence from Australia, 

 354 



Uniformitarianism, 340 



Unio, 77. (See also Clams.) 



Unisexual reproduction, 181 



Unit characters, 252 



Universal symmetry, 106 



Urea, 147, 151; elimination of, 152 



Ureter, 120, 127, 130, 152 



Urethra, 127, 132 



Urinary bladder, 120, 127; muscles of, 156 



Urine elimination, 152 



Uriniferous tubules, 126, 127, 152 



Urinogenital system, 130; of female frog, 

 130, 131; in female mammal with 

 bicornuate uterus, figure of, 133; in 

 lizard, 195; of male frog, 131, 132; 

 in mammals, 131-133 



Uroglena, 87 



Use, in evolution, 359 



Use and disuse, 21; in evolution, 359 



Uterus, 129, 130; form of, 132, 195; in a 

 mammal, 196 



Vacuole, 32, 33, 56; contractile, 33, 59; 



food, 33; pulsating, 33 

 Vagina, 129, 130, 132 

 Vagus nerve, 163 

 Variation, 23, 239, 256; fluctuating, 344; 



in mitosis, 76-78 

 Variety, in classification, 264 

 Vasa deferentia, 133; of earthworm, 



119 

 Vasa efTerentia, 120, 129, 131 

 Vas deferens, 128, 129; opening of, 128 

 Vegetation, in environments, 292, 293, 



294, 305 

 Vegetative pole, 213, 215 

 Veins, 123; muscles of, 156 

 Venous blood, oxygen in, 149 

 Ventral, 105 

 Ventral horn, 142 



Ventral nerve cord, of earthworm, 119 

 Ventral root, of spinal nerve, 229 

 Ventricle, 124; of heart, 120 

 Vermilion eye color in Drosophila, 344 



361 

 Vertebra, 136 



Vertebral column, 135; parts of, 136 

 Vertebrata, classified, 270, 273 

 Vertebrates, classified, 273; digestive 



systems in, 117-120; hermaphrodi- 



tism in, 190; organogeny of, 223-235; 



origin of germ cells in, 209, 210; 



oviparous and viviparous, 198; parts 



fossilized, 311; skeleton of, 135 

 Vertebrate skeleton, figure of, showing 



regions, 135 

 Vertebrate type, 17 

 Vesalius, Andreas, 10, 11, 15 

 Vesicle, seminal, 128 



Vesicula seminalis, 120, 128; base of, 128 

 Vestigial wing in Drosophila, 345 

 Vibracularia, 100, 101 

 Vicq d' Azyr, 17 



Vicuna, 329. (See also Auchenia.) 

 Vitamines, 53 

 Vitelline duct, 130 

 Vitelline gland, 129; duct of, 129 

 Vitelline reservoir, 129 

 Viviparity, blood supply in, 196; defined, 



195, 196; dominant where, 205; in 

 Hydra, 195; in insects, 195; in in- 

 vertebrates, 198; in jellyfishes, 195; 

 locus and nutrition of embryo in, 



196, 197; parental care in, 201; in 

 plant lice, 195; relation to place of 

 fertilization, 198; in shark, 196, 197; 

 true viviparity, 195, 197; in verte- 

 brates, 198 



Vocal cords, 123 



Voluntary motions, 162, 163 



Volvocales, 87 



Volvox, 87, 90, 91, 93, 106, 176; proto- 

 plasmic strands in, 34; reproduction 

 of, 190 



Volvox aureus, 90 



Volvox perglobator, 90 



Volvox rousselettii, 90 



Von Mohl, Hugo, 26 



Vorticella, 65, 85, 87, 171, 180; reproduc- 

 tion of, 190; stalk of, 155 



Vorticellida>, 93 



de Vries, Hugo, 344 



Wading birds, birth stages in, 201 



Wales, ancient men of, 336 



Wall, 42 



Wallace, Alfred Russel, 342 



Walnut comb, 362 



Warmth, 163 



Wasps, 181; mimicry in, 280 



Water, brackish, 316; course of, through 



mouth, pharynx and gill slits, 227; 



depth of, an environmental factor, 



