Roux, W., 141 ff. _Saccharomyces_, 36; _cerevisiæ_, 60 _Sacculina_, 216 ff. Sachs, 88 v. Sachs, J., 145, 154 ff., 159, 161, 184 _Salamandra maculosa_, 339 Salkowski, 352 Salts required for life, 306 ff. Sansum, W. D., 64 _Schizophyceæ_, 21 Schleip, W., 213 Schoenbein, 358 Schottelius, 334, 337 Schroeder, 14, 33 Schultze, O., 141 Schütze, 55 Schwann, 33 Schwarzschild, 34 Secretions, internal, 145, 155, 157 Self-digestion, 350 ff. Self-sterility, 89 ff. Senescence, 367 _Sequoia_, 31, 368 Setchell, W. A., 165, 287 Sex, of parthenogenetic frogs, 125; of twins, 211 Sex chromosome, 199 ff. Sex determination, cytological basis of, 198 ff.; physiological basis of, 214 ff. Sexual characters, 198 ff. Shibata, 93 Shull, A. F., 214, 224 _Sicyonia_, 193 Side-chain theory, 88, 188 Smith, Geoffrey, 159, 217 Smith, Graham, 58 Spain, K. C., 188 Spallanzani, 33 Species, chemical basis of, 40 ff.; specificity of, 41 ff.; incompatibility of, not closely related, 44 ff. Species specificity, determined by proteins, 63, 68, 348; apparently not by nucleins, 69 Specificity, of grafted tissues, 47; of spermatozoa, 48; of blood sera, 53 ff.; in fertilization, 71 ff.; of activation of sperm by eggs, 80 ff. _Spelerpes_, 320 Spermatozoa, fertilization of eggs by, 72 ff.; activation by eggs of, 80 ff.; agglutination of, 82 ff.; cluster formation of, 83; chemotropism of, 92 ff.; cultivating of, 126 ff.; chromosomes of, 198 ff. _Spirographis_, 260 _Spondylomorum_, 277 Spontaneous generation, 33, 38 Spooner, G. B., 134 Standfuss, 303 _Staphylococcus pyogenes aureus_, 36 Steffenhagen, K., 55 Steinach, E., 225 ff., 254, 343 Stereotropism, 178, 187, 283 Stevens, Miss, 68, 199 Stimulus, 196 Stockard, 322, 340 Strassburger, 260 Streaming as means of egg differentiation, 145, 146 _Strongylocentrotus franciscanus_, 50, 52, 75, 81 ff., 103, 247 _Strongylocentrotus lividus_, 129 _Strongylocentrotus purpuratus_, 52, 73 ff., 81 ff., 94, 98 ff., 103, 108, 109, 111 ff., 137, 191, 246 ff., 293 ff., 364; larvæ of, 49 ff. Sturtevant, A. H., 229 ff. Styela, 146 Sulphur bacteria, 19 ff. Supergenes, 5, 9, 136, 319 Sutton, W. S., 68, 233 ff. Synthesis of living matter, by micro-organisms, 15 ff.; by enzymes, 24 ff. Synthetic action of enzymes, 23 ff., 38 _Tænia_, 212 Talbot, 262 Tammann, 291 Tanaka, 243 Taylor, A. E., 27, 69 ff. Tchistowitch, 54 ff. Teleost fish, crosses of, 6 ff., 345 Temperature, effect on heliotropism, 280; upper limit for organisms, 287 ff.; effect on life, 288 ff.; on butterflies, 303 ff.; adaptation to, 334 ff.