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INDEX OF SUBJECTS 



Plasma-stains, 28, 242. 

 Plasmosome, 24. 

 Plasome, 22. 



Plastids, 37; of the ovum, 98, 160; of the 

 spermatozoid, 107; conjugation of, 169; 

 in fertilization, 170, 171 ; independence, 

 211. 



Plastidule, 22. 



Polar bodies, 131 ; nature and mode of 

 formation, 175-180; division, 179; in 

 parthenogenesis, 202-205. 



Polarity, of the nucleus, 26, 215 ; of the cell, 

 38; of the ovum, 278, 279, 298; determi- 

 nation of, 285, 287, 322. 



Polar rings, 121, 150. 



Pole-plates, 64. 



Pollen-grains, formation, 59; division, 195. 



Pollen-tube, 106, 161. 162. 



Polyclades, cleavage, 313. 



Polygordius, cleavage, 269. 



Polyspermy, 140, 147; prevention of, 148. 



Polystomclla, regeneration, 249, 250. 



Porcellio, amitosis, 82. 



Predelineation, 297. 



Preformation (see Evolution). 



Principal cone, 71. 



Promorphology (see Cleavage, Ovum). 



Pronuclei, 151. 



Prophase, 47. 



Proteids, 239. 



Prothallium, 160; chromosomes in, 196. 



Protoplasm, 3, 15; structure, 17, 212; chem- 

 istry, 238. 



Protoplast (see Plastid). 



Pseudo-alveolar structure, 19, 94. 



Pseudo-reduction, 61, 193, 194, 197, 205. 



PierotJ-achea, germ-nuclei, 135, 137, 153. 



Ptychoptera, spireme-nuclei, 25. 



Pygtzra, formation of spermatozoon, 123. 



Pyrenin, 25, 29. 



Pyrenoid, 98. 



Pvrrochoi'is, tetrads, 188. 



(Juadrille of centres, 157. 



Reduction, general, 173; general outline, 

 174; parallel between the two sexes, 180, 

 182; theoretical significance, 182-185; 

 detailed account, 186-193; in plants, 

 195-197; Strasburger's theory of, 196; 

 in unicellular forms, 198; by conjugation, 

 199; modes contrasted, 206. 



Regeneration, 293, 294; Weismann's theory, 

 305; in frog-embryo, 307; nature of, 323; 

 in coelenterates, 225; of lens, 329. 



Rejuvenescence, 129, 165. 



Ren ilia, ovum, 96, 145. 



Rhabdonema, amitosis, 81. 



Rhynchelmis, fertilization, 142; cleavage, 



Sagitta, number of chromosomes, 49; pri- 

 mordial germ-cells, no; germ-nuclei, 135; 

 sperm-aster, 140. 



Salamander, epidermis, 2, 16, 20; sperma- 

 togonia, 15, 16, 234; nuclei, 24; mitosis 

 in, 54-56, 60; pathological mitosis, 69; 

 leucocytes, 72; spermatocyte, 78; amito- 

 sis, 82; spermatozoa, 125; tetrads, 191, 

 192. 



Sargiis, pigment-cells, 73. 



Segmentation (see Cleavage). 



Selaginella, spermatozoids, 145. 



Senescence, 130, 165. 



Sertoli-cells, 1S3, 208. 



Sex, 7; determination of, 109; nature of, 

 130; Minot's theory of, 183, 208. 



Siphonophores, amitosis, 83. 



Soma, 1 1 . 



Somacule, 22. 



Somatic cells, 88; number of chromosomes, 

 176. 



Spermary, 89. 



Spermatid, 122, iSo ; development into 

 spermatozoon, 122-126. 



Spermatocyte, 122, 180; of Ascaris, 180, 

 225. 



Spermatogenesis (see Reduction), 173; gen- 

 eral outline, parallel with oogenesis, iSo- 

 182. 



Spermatogonium, 122, 180; early history, 

 194; of salamander, 234. 



Spermatozeugma, 106. 



Spermatozoid, structure and origin, 106, 

 126; in fertilization, 145, 160. 



Spermatozoon, discovery, 7; structure, 98; 

 essential parts, loi ; giant, 105; double, 

 106 ; unusual forms, 106; of plants, 107 ; 

 formation, 123 ; in fertilization, 131, 136; 

 entrance into o\'um, 145; physiological 

 significance, 90, 141, 171. 



Sperm-centrosome, 99, loi ; position, 123; 

 in fertilization, 135, 138, 141, 143. 144. 

 156-159, 171. 



Sperm-nucleus, 99, loi, 103; origin, 122; 

 in fertilization, 132, 153; rotation, 137; 

 path in the egg, 151 ; in inheritance, 252, 



257- 

 Sphixrechinus, fertilization, 143 ; number of 



cells, 291 ; hybrids, 258. 



Spindle (see Amphiaster, Central spindle), 



49. 57; origin, 48, 53, 74, 214; in Pro- 



