Index 



Sexual dimorphism, 364 

 Sexual selection, 274, 364, 366 

 Shakespeare, William (15 56-1616), 434 

 Smith, William (1769-1839), 27, 29, 31 

 Soma plasm, 311, 313, 314, 315, 371 

 Special creation, xiii, 122, 130; argument 



for. III 

 Specialization, 86; and evolution, 188 

 Species, 51, chap. 4; an abstraction, 65; 

 and varieties, 175; as entities, xiii, 122, 

 181; conception of, 275; definition of, 

 373; extinction of, 66; fixity of, 163; 

 modification of, 275;; transformation of, 

 281, 286, 288; transmutation of, 276, 

 283, 293 

 Spencer, Herbert (1820-1903), 308, 310, 



314. 318 

 Sport, 183 



Stability, relativity of, 374 

 Stature, environment and, 219; heredity 



and, 213 

 Stockard, Charles R. (1879- ), 172, 



326 

 Stratification, 24 

 Struggle for existence, 154, 156, 159, 192, 



33i> 337. 338» 360 

 Suarez, Francisco (i 548-1617), xiii, 297 

 Succession, and descent, 48, 227, 228; of 



diverging species, 34 

 Supernumerary digits, 218 

 Swamping, 191, 305. 3 59. 360 

 Synthesis, in physiology, 424 



Tail, human, 142; in human beings, 204, 



205; in man, 205 

 Teleology, 410, 421, 427, 446, 453, 454 

 Temperamental diflferences, 215 

 Temperature, effect on development, 170 

 Thayer, Abbot H. (1849-1921), 342 

 Theories of evolution, 411, 429 

 Thomson, J. Arthur (1861- ), 3^9 



Throw-back, 248 

 Thymus, 102 

 Thyroid, 212, 214 

 Thyroxin, 415 



Tower, William L. (1872- ), 163 

 Transcendentalism, 428 

 Transformation of species, 33 

 Transmission of acquirements, 318 

 Tree of life, 69 

 Tri-hybrid, 244 

 Trilobite, 29, 30, 35, 115, 190 

 Trochophore, 136, 137 



473 



Tropics as man's original home, 196 

 Tschermak, Erich (1871- ), 288 



Twins, 6^ 



Ungulates, 116 



Uniformitarianism, 284, 285 



Uniformity, 13 



Unit character, 247, 248 



Unity of life, 95 



Use and disuse, 174 



Vaccination, 459 



Variability, 146; among primates, 202; 

 and evolution, 192; human, 216; in 

 embryos, 207 



Variation, 74, 293; climatic, 168; con- 

 tinuous and discontinuous, 163, 334, 

 375> 37^5 378; emotional, 220, 221; 

 fluctuating, 334; individual, 146, 156, 

 157, 160, 162, 163; intellectual, 220, 

 221; kinds of, 159; physiological, 162, 

 220; regional, 168; sources of, 163, 368 



Vertebrates, origin of, 138 



Vestigial structures, 98, 119 



Virchow, Rudolf (1821-1903), 198, 288, 

 313, 450, 458 



Vitalism, 410, 427 



Vitamin, 116 



de Vries, Hugo (1848- ), 183, 184, 



288, 378, 379, 380, 383, 392, 394, 396, 

 397, 400; criticisms of, 382 (portrait 

 facing p. 384) 



Wagner, Moritz (18 13-1887), 360 

 Wallace, Alfred R. (1823-1913), 331, 



366, 394, 399 (portrait facing p. 337) 

 Weathering, 21, 25 

 Weissman, August (1834-1914), 294, 310, 



311. 313. 314. 315. 317. 371. 372, 378, 

 383, 394 (portrait facing p. 320) 



Weldon, W. F. R. (1861-1906), 348 



Whale, 16, 116, 132, 134 



Wiedersheim, Robert (i 848-1923), 102 



Wishful thinking, 449 



Wolf, 34 



Worm, 303; embryos of, 137; develop- 

 ment of, 136 



X-rays, 416; and chromosomes, 395 



Zebra's coat pattern, 395 

 Zygote, 254, 256 



