INDEX OF SUBJECTS 



48: 



Sargus, pigment-cells, 103. 

 Scyllium, 263. 



Segmentation (see Cleavage). 

 Selaginelln, spermatozoids, 197. 

 Senescence, 179. 

 Sepia, spindle, 81. 

 Sertoli-cells, 284. 



Sex, 9; determination of, 144; Minot's the- 

 ory of, 243. 

 Siphonophores, amitosis, 117. 

 Soma, 13. 

 Somacule, 291. 

 Somatic cells, 122; number of chromosomes, 



233- 



Spermary, 123. 



Spermatid, 161, 163; development into sper- 

 matozoon, 164. 



Spermatocyte, 161, 241. 



Spermatogenesis (see Reduction), 234; gen- 

 eral outline, parallel with oogenesis, 241. 



Spermatogonium, 161, 241. 



Spermatozeugma, 142. 



Spermatozoid, structure and origin, 142, 

 172; in fertilization, 217, 221. 



Spermatozoon, discovery, 9; structure, 134; 

 essential parts, 135; giant, 141; double, 

 142; unusual forms, 142; of plants, 142; 

 formation, 160; in fertilization, iSl, 192; 

 entrance into ovum, 197. 



Sperm-centrosome, 135, 164-171; in fertili- 

 zation, 192, 211-215, 221. 



Sperm-nucleus, 135; origin, 164-171; in 

 fertilization, 182, 190; rotation, 188; path 

 in the egg, 202; in inheritance, 353; 

 chemistry, 334. 



SphcTrechinus, fertilization, 193, 210; num- 

 ber of cells, 389; hybrids, 353; regenera- 

 tion, 393. 



Spindle (see Amphiaster,Central Spindle), 68; 

 origin, 72, 79,82; in Protozoa, 90; conjuga- 

 tion of, 227; nature of, 316; position, 375. 



Spireme, 65. 



Spirochona, mitosis, 90. 



Spirogyra, nucleolus, 67 ; amitosis, 1 19 ; 

 conjugation, 229; reduction, 280. 



Spongioplasm, 25. 



Spontaneous generation, 7. 



Stem-cells, 148. 



Stenior, regeneration, 342. 



Siylonychia, senescence, 224. 



Stvpotaidon, mitosis, 82. 



Surirella, 94. 



Symbiosis, 53, 292. 



Synapta, cleavage, 364. 



Syncytium, 59. 



Teloblasts, 371, 390. 



Telophase, 71. 



Tetrads (Vierergruppen), 238; origin, 246; 

 in Ascaris, 241, 253; in arthropods, 248; 

 ring-shaped, 248; in amphibia, 259; ori- 

 gin by conjugation, 257; formulas for, 

 247. 



Tetramittis, 40, 92. 



T/ialassema, spindle, 81 ; fertilization, 193, 

 194, 213; reduction, 259, 263; centro- 

 some, 321; attraction-sphere, 325. 



Thalassicolla, experiments on, 344. 



Thysanozoon, 212, 259, 326. 



Tonoplast, 53. 



Toxopneustes, cleavage, 10; mitosis, 107; 

 ovum, 126; spermatozoon, 134; fertiliza- 

 tion, 188; paths of germ-nuclei, 202; 

 polar bodies, 114; double cleavage, 355. 



Trachelocerca, diffused nuclei, 40. 



Trillium, 269. 



Triton, 140, 212, 263, 277. 



Trophoplasm, 322, 401. 



Tubularia, regeneration, 430. 



Tunicates, egg-axis, 379; cleavage, 381. 



Unicellular organisms, 5; mitosis, 88; con- 

 jugation, 222; reduction, 277; experi- 

 ments on, 342. 



U}iio, centrosome and aster, 314; cleavage. 

 381. 



Urostyla, 40. 



Vacuole, 50, 53. 



Vanessa, ovarian egg, 153. 

 Variations, 1 1 ; origin of, 433. 



Vatuheria, membrane, 348. 

 Vitalism, 394, 417. 



Vitelline membrane, 132; of egg-fragments, 

 132; formation of, 198; function, 199. 



Volvox, germ-cells, 133. 



Vorticella, conjugation, 226, 



Xiphidium, 271. 



Yellow cells (of Radiolaria), 53. 

 Yolk (see Deutoplasm), 152. 

 Yolk-nucleus, 155. 

 Yolk-plates, 131. 



Zamia, 173, 221. 

 Zirphaa, 259, 263. 

 Zwischenkorper (mid-body), 71. 

 Zygneiiia, membrane, 346. 

 Zygospore, 228. 



