Septobasidiwn, 74 



Sequoia, 252 



Sequoiculendron, 252 



Sequoias, 61, 263 



Sex, differentiation of, 47, 172 



Sex-chromosome meclianisms, 178 



multiple, 178 



XO type, 48 

 Sex cfiromosomes, 28, 32, 47, 175 

 Sex determination, 200, 201 

 Sex linkage, 47 

 Sex ratios, 96 

 Sexual isolation, 242 

 Sexual reproduction, 166 

 Sexuales, 205, 206 

 Sexuality in man, 282 

 Sexuparae, 205, 206 

 Sheppard, 131, 133-135, 148, 159 

 Shigella dtjsenteriae, 164 

 Sibling species in butterflies, 220, 244 

 Sickle-cell anemia, 145, 230 

 Significance, statistical, 128n. 

 Silene, 147 

 Silkworms, 41 

 Simpson, G. G., 128ri., 259-265, 274, 275, 



277 

 Sinnott, E. W., 16, 55 

 Siphonales, 167 

 Sitta europaea, 128 



neumayer, 229 



tephrotwta. 229 

 Size, overall body, increase in, 274, 275 

 Slobodkin, L. B., 88, 248 

 Sloth, 84 

 Sloth moth, 84 

 Snails, polymorphic land, 133-136 



{See also Cepaea) 

 Snakes, 265 

 Sneath, P. H. A., 314 

 Social behavior, evolution of, in bees, 158, 



159 

 Social hierarchy, 80 

 Social insects, 74, 80, 158 

 Social sanctions, 288 

 Sokal, R. R.,314 



Somatic pairing of chromosomes, 49 

 Song thrush, 128, 133 

 Speciation, 211,230 



allopatric, 247 



horizontal, 259 



sympatric, 247, 248, 311 



vertical, 259 



Species, 211,272, 298,302 

 Species swarms in fishes, 220 

 Spergula, 147 

 Sphenodon, 252, 256 



ptinctatus, 251 

 Spindle, 27 

 Spindle fibers, 26 



Spiralization of chromosomes, 28, 30 

 Spleenwort, 194 

 SpUtting, 259, 261 

 Spontaneous generation, 5 

 Sporogenesis, 168 

 Sporophyte generation, 168, 199 

 Sporozoa, 168 

 Spotted flycatchers, 128 

 Spuhler, 123 

 Stag beetles, 275 

 Standard deviation, 52 

 Stationary frequency distributions, 114, 115 

 Stebbins, G. L., 88, 159, 167, 170, 171, 183, 



185, 191, 194, 195, 207, 249, 277 

 Stebbins, R.C., 219, 221 

 Storksbm, 84 

 Streams, 248, 249 

 Strepsiptera, 267 

 Styx. 252 



infernalis. 251 

 Succession, ecological, 86 

 Succulent plants, convergence in, 270 

 Sunflower, 241 



Supergenes, 144, 148, 175-177, 183 

 Supernumerary chromosomes, 186 

 Survivorship curves, 260, 261, 263 

 Swallowtail butterfly, 147 

 Swanson, C. P., 35 

 Switch genes, 52 

 Sycamore, 75 

 Symbiosis, 74, 84 



Sympatric speciation, 247, 248, 311 

 Sympatry, 240 

 Synapsis of chromosomes, 32, 41, 176, 187, 



190 

 Syngamy, 165, 166 



Taboos, 291 



Tachytely, 261, 263, 265, 267, 272 

 Tadpoles, 63 

 Tanager-like finch, 225 

 Tarsiers, 283 

 Tasmanian devil, 265 

 Tasmanian wolves, 265 



345 



