550 



INDEX 



Skull (Continued) 

 of thecodonts, 178 

 of Therapsida, 171, 176, 178, 220 

 See also Brain 

 Sloth, 27, 260, 261 

 Smith, E. A., 339, 344, 345, 363 

 Smith, H. M., 78, 423,426 

 Smith. H.W.. 108 

 Smith,J.L. B., 159, 172 

 Smith, N., 197, 198, 200-201, 205, 217 

 Snail, 137, 147, 151,284,285 

 first air-breathing, 155 

 land, 287 



and protective coloration, 370 

 tree, 283,315-316 

 Snakes, 777, 289 

 vestiges in, 43 



See also Reptiles 

 Snapdragon, Mendelian inheritance in, 



379 

 Snodgrass, R. E., 44 

 Snyder, L. H., 402 

 Social Darwinism, 520 

 Social evolution, 517-518, 519-522 

 Social inheritance, 519 

 Social insects, see Insect 

 Society, contribution to, 355 

 Sodium chloride, see Salt 

 Solecki, R., 278 

 Solo man, 244 

 Solomon Islands, 485, 486 

 Somites, in fishes and Ambly stoma, 55-56 

 in human embryos, 54, 55-59, 58, 59 

 Songs of birds, see Birds 

 Soul, human, 6. 219 

 South African ape-man, see Australo- 



pithecines 

 South America, animals of, 119-120, 258 

 261, 260, 266-267, 270-272, 291, 

 292 

 Space restrictions and population size, 



353 

 Sparrow, 293 



Spassky, B., 454, 455, 456, 482 

 Spatial isolation, see Isolation, geo- 

 graphic 

 Special creation, see Creation 

 Specialization, 153, 356 

 dangers of, 300, 304 

 in nutrition, 86 

 Speciation, 484-491 



instantaneous, see Polyploidy 

 Species, 314-320, 350 



attributes of: structural difference in, 

 249, 314-316, 444-445; reproductive 

 isolation, see Isolation, reproductive 

 definition of, 232, 307 

 differentiated from races, 250-255 



Species (Continued) 



"elementary," 337 



origin of, 358-359, 474 

 See also Speciation 



polymorphic, 366, 375-376 

 Spencer, W. P., 446, 449 

 Sperm, 332, 381, 382, 385, 386, 387, 388, 

 394-395, 399. 400 



See also Germ cell; Germ plasm; 

 Mendelian inheritance 

 Spermatid, 381, 382, 383, 386, 395 

 Spermatocyte, primary, 381, 382, 383, 

 386, 387, 394, 395 



secondary, 381, 382, 383, 386, 395 

 Spermatogenesis, see Meiosis 

 Spermatogonium, 380-557, 382, 394 

 Spider, 137, 147, 155 

 Spiderwort, 478, 479 

 Spiess, 465 

 Spinal cord, embryonic, 54, 58, 63 



of Stegosauria, 183 

 Spindlefiber, 380,i57, 396 

 Spines, 120 



neural, 171 



of Stegosauria, 183 

 Splint bone, 23, 43 



See also Limbs, of horse 

 Sponge, 94, 137, 146, 148 

 Sports, see Mutations 

 Squid, 151, 176 

 Squirrel, 27, 117 



color phases in, 375 



flying, 28 



reproductive isolation in, 248 

 Starch, see Carbohydrates 

 Starfish, 47, 102, 150 

 Stature, of australopithecines, 233 



of Neanderthal man, 243 



of Pithecanthropus, 238 



variability in, 252 



See also Body size 

 Stebbins, G. L., Jr., 420, 426, 477, 480, 



483,501,507 

 Stegocephalia, see Labyrinthodontia 

 Stegodon,211, 215 

 Stegosauria, 183 

 Steinheim people, 249 

 See also Skull 

 Steinmann-Doderlein, 188 

 Sterility, see Fertility, lack of 

 Sternum, of birds, 187 



of pterosaurs, 186 

 Stewart, T. D., 244, 257 

 Stomach, embryonic, 63 

 Storer, T. I., 39, 162 

 Strata, 130-134, 133 

 Straus, W. L., Jr., 227, 228, 243, 257 

 Streptomycin, 401, 451, 452 



