INDEX 



549 



Selection pressure, see Natural selection, 



intensity of 

 Sellards. E. H.. 140. 142 

 Semilunar fold, 42 

 Senescence, racial, 153, 175 

 Septum, see Shell 

 Serial homology, see Homology 

 Serological tests, 109-126. 324-325 

 Serpula, 103 

 Serum, 109 



Serum proteins, homology of, 110-113 

 Seton, E. T.. 308. 328 

 Sewall Wright effect, see Drift, genetic 

 Sex characteristics, primary, 491 



secondary, 491-494 

 Sexual isolation, see Isolation, reproduc- 

 tive 

 Sexual selection. 350. 472. 475-476. 491- 



494 

 Seymoiiria. 167. 168 

 Shanidar man, 244 

 Shark, 156, 157, 161 

 aortic arches of, 61 

 convergent evolution in. 30 

 embryonic development of, 46 

 gills of, 60, 61 

 heart of, 61 



osmotic regulation by. 99, 100 

 respiratory mechanism of, 60-6i 

 shell-crushing, 137, 164 

 Sheep, classification of, 115 

 clavicle of, in embryo, 75 

 color in, 349, 433 

 limb of. see Limbs 

 mountain, 264 



See also Ancon ram; Serological 

 tests 

 Shell, of brachiopods, 147 

 egg, 168, 769 



of molluscs, 147, 151-152, 154 

 septum of, 151, 154, 173. 175 

 suture of, 151-152, 154, 155, 159, 

 173,174, 175 

 See also Fossils 

 Shell fish, see Mollusca 

 Shell membranes, 168, 769 

 Sheppard, P. M.. 370, 374, 447, 449 

 Shrew, 26, 27, 192 



tree, 220, 221,222, 224 

 See also Insectivora 

 Shrimp, brine. 148 

 Sibley. C. G., 121, 125, 477, 480, 481, 



483 

 Sicher. H., 232, 256 

 Sicklebills, see Drepanid birds 

 Sight, in birds, 187, 366-368, 370-373 

 in predators, 364-370 

 in pterosaurs, 186 



Silurian period, 137. 153-154 

 Simian gap, 230. 2i/, 234 

 Simian shelf, 230-231 

 Similarity, in blood plasma, 94-95 

 in chemical composition, 79-82, 105 

 in classification, see Classification 



explanation of, 20-26, 313 



in metabolism, 84-86. 90 



origin of. 24—25. 313 



of physiology, 82-84 



See also Analogy; Homology 

 Simons. E.L., 227, 228, 257 

 Simpson, C. T., 316, 328 

 Simpson. G. G.. 13. 15. 17, 19, 116, 125, 

 142, 172, 190, 192, 204, 206, 217, 

 221, 257, 261, 265. 266. 278, 291, 

 305. 328. 363, 410, 411, 412, 421, 

 424, 425, 426, 449, 482, 483, 496, 

 501, 502, 504, 505, 506, 507, 518, 

 523 

 SinatUhropus. see Pithecanthropus 

 Sinnott, E. W., 402. 419. 426. 478, 483 

 Skin and genetic assimilation, 422-423 

 Skin color, see Pigment 

 Skull, of amphibia, .^7 



of australopithecines, 233-25-^ 



of cotylosaur, 176 



of Cro-Magnon man. 245 



of Diapsida. 116-178 



of Dinotherium. 212. 27-^ 



Ehringsdorf, 241, 242 



of elephant, 207, 208. 209 



of Equiis. 199 



Fontechevade, 241 



of Gomphotheriiim, 213, 275 



of gorilla, 2iO 



growth of, see Allometry 



of Hot7io sapiens, 229, 230, 234 



of horse. 799-200. 408. 409, 410. 412, 

 413,417 



of Hyracotherium, 199, 201 



of mammals, i/, 190 



of mastodon, 2 1 3-214, 275 



of Merxchippiis. 199, 205 



of Mesohippus, 199. 203 



of Moeritheriiim, 210, 272 



of Neanderthal man, 243 



of Paleoniastodon, 211, 212 



of Phiotnia, 2\2. 213 



of Pithecanthropus, 239 



of Pliohippus, 206 



of reptiles. 31, 170, 171-172, 190 



of Stegosauria, 183 



Steinheim. 241 



structure of, homology in, 30-32 



Swanscombe, 241 



of Synapsida, 178 



of Tasmanian aboriginal, 234 



