Index 



385 



Salmonella, 67, 68 



Saltation, 90 



Salt marsh snails, 246 



Salvia, 182 



Sand areas, 275 



Santa Cruz jay, 171 



Saturn, 15 



Schistocerca gregaria, 130 



Schleiden, 2 



Schultze, 2 



Schwann, 2 



Sea level changes, 329 



Sea pens, 141 



Segregation, chromosome, 82 



cytoplasmic, 82 

 Selection, by environmental factors, 

 101 



by internal factors, 100 



centrifugal, 108 



centripetal, 108 



complex pattern of, 104 



direction of, 108 



experimental, 100 



intensive, 100 

 Selection pressures, competitive, 224 



reticulate, 342 

 Semi-desert biomes, 286 

 Sex, determinants, 66 

 Sex, evolution of, 55 

 Sexual isolation, 169 



development of, 162 

 Shift in geographic position, 131 

 Sial, 19 

 Sickle-cell, 102 

 Silicates, 16 

 Silurian, 57, 263 

 Sima, 19 

 Sitta, 221 



Skunk cabbage, 158 

 Slipher, 12 



Smooth green snake, 158 

 Social parasitism, 217 

 Solar system, 14 

 Somatic polyploid mutation, 199 



Sortosa, 152 



Species and lower categories, 202 

 Species composition, change in, 239 

 Species fission, by colonization, 170 



and time, 172 

 Species, 114, 115 



adaptive change, 140 



allopatric, 166 



as an adaptive unit, 135 



as a physical unit, 122 



biological characteristics, 119 



congregation of, 211 



definition, 117, 206 



ecological characteristics, 119 



flocks, 183 



fossil, 117 



genetic composition, 135 



hybrid, 192 



identification characteristics, 118 



immutable, 2 



increase in number, 153, 319 



interbreeding characteristics, 138 



mixing, 250 



number of, 207 



population, 127 



range, 122, 131 



recognition, 114 



reproductive characteristics, 118 



"successful," 134 



sympatric origin, 241 



variability, 139 

 Sperm nuclei, 52 

 Sphagnum bog, 267, 276 

 Spherules, 46 

 Spindle, 31 



Spruce budworm, 87, 278 

 Stars, evolution of, 13, 338 



twin, 15 

 Steady state theory, 12, 13 

 Steroids, 35 

 St. John's wort, 289 

 Straight-line selection, 109 

 Stream communities, 262 

 Subclimax communities, 266, 315 



and time, 270 



change in, 284 



