448 



INDEX 



Selaginella, spore coat, 194, 195 

 Senescence, 63, 136 ff. 

 Sequoia (conifer), 294, 295 

 Sex, chromosomes, 358$"., 380 ff. 



determination of, 354 ff., 373 ff. 



intergrades, 370 ff. 



linkage, 380 ff. 



Mendelian interpretation of, 366 



practical control of, 376 



quantitative theory of, 370 



ratio, alteration of, 367 ff. 



reversal, 370 ff. 

 Sex-limited characters, 381 

 Sex-linked characters, 381 

 Sexual reproduction and rejuvenescence, 



137 



Shaffer, 118, 120, 121 

 Sharp, 64, 87, 90, 92, 147 ff., 160, 176, 



225, 242, 254 

 Shaw, 91, 316 



Shull, A. F., and Ladoff, 368 

 Shull, G. H., 382 

 Sida (crustacean), 319 

 Sieve tube, 28 

 Silica, 135, 194 

 Silk gland, 66 



Simocephalus (crustacean), 371 

 Simplex chromosome group, 340 

 de Sinety, 358 

 Siphoneae, 59 

 Slime globules, 203 

 de Smet, 150, 159, 160 

 Smilacina (angiosperm), 236, 239 

 Smith, B. G., 159, 160, 278, 279 

 Smith, G. M., 108 

 Smith, H. L., 79 

 Sokolow, 119 

 Sol, 35 

 Somatic mitosis, 143 ff. 



comparison with heterotypic, 228 



pairing of chromosomes, 256 



segregation, 352, 395 

 Sordaria (fungus), 81 

 Sorodiscus (slime mold), 208, 209 

 Spallanzani, 14 

 Species, origin of, 347 

 Specificity of chromosomes, 162, 250 

 Spek, 189 



Spencer, 48, 49, 398 

 Spermatia, 312 

 Spermatid, 87, 220 

 Spermatocyte, 220, 235 

 Spermatogenesis, in animals, 95, 96, 220 



Spermatogenesis, chondriosomes in, 119, 

 120 



in man, 361, 362 



in plants, 86 ff. 

 Spermatogonia, 220 

 Spermatozoids, 86 ff., 288 ff., 293, 294 

 Spermatozoon, discovery, 14 



in fertilization, 277 ff. 



in heredity, 324, 328 



structure, 273, 275 



types, 274 



Sphacelaria (brown alga), 79, 186 

 Sphcerechinus (sea urchin), 325-327 

 Sphcerocarpos (liverwort), 355, 364, 365, 



372, 375 



Sphceroplea (green alga), 222 

 Sphcerotheca (fungus), 290 

 Sphserraphides, 135 

 Sphagnum (moss), 248 

 Spherome, 122 



Spinacia (angiosperm), 248, 256 

 Spinax (fish), 237 

 Spindle, 145, 147, 154, 175 

 Spiral stage of chromosome, 150, 152, 155 



wall thickening, 28, 192 

 Spireme, 145, 150, 153, 154, 232, 238 



in fertilization, 300, 301 



in heterotypic prophase, 241-243 

 Spirogyra (green alga), amitosis, 211 



conjugation, 288 



cytokinesis, 186 



enucleated cells, 69 



mitosis, 209 



nuclear fusion, 14, 273 



plastid, 104 



pyrenoid, 104, 108 



reduction, 222 



Spirostomum (protozoan), 61, 62 

 Spitzer, 70 



Splitting of chromosomes, in first em- 

 bryonal division, 295, 300; in matu- 

 ration, 236, 239, 242, 258; in somatic 



mitosis, 153, 242, 392 

 Spoehr, 41 

 Spore membrane, 195, 196 



tetrads, 223-225, 355 

 walls, 194 

 Sporocyte, 225, 232 



Sporodinia (mold fungus), 110, 187, 290 

 Sporogenesis, in various plant groups, 

 222 jf. 



behavior of plastids in, 114 



without reduction, 315, 316 



