294 



INDEX. 



Plasmodium, 141, 142 



Platneron sex-cells in snail, 118 



Ploss on embryonic hermaphroditism, 

 28, 61 



Polar globules, 99-101, 167-171 



Pollen-grain, 212, 213 



Polyspermy, 29 



Polystomum, 224 



Population question, 267-274 



Precocious reproduction, 191, 192, 225 



Preformation, theory of, 79, 80 



Primary sexual characters, 3 



Protococcus, 120 



Protomyxa, 141 



Protoplasm, metabolism of, 82, 83, 

 115, 116; in fertilization, 149, 150; 

 mechanics of, 206, 207 ; in relation 

 to cell-division, 206, 207 



Protozoa contrasted with Metazoa, 51, 

 84, 85; illustrating cell-phases, 112- 

 115; conjugation of, 139-142; asex- 

 ual multiplication, 178; immortality 

 of, 85, 155, 238, 239; alternation of 

 generations in, 193 



Puberty, 223 



Purkinje, 81 



Pycnugonid, male with young, 252 



Rate of increase, 261, 263 



Rate of reproduction, 261-275 



Rauber on somatic and reproductive 

 cells, 88 



Regeneration, 176 



Renroduction, processes of, 129, 199; 

 theory of, 203, 243 ; origin of, 215, 

 216 ; in relation to environment, 217- 

 219; nemesis of, 217, 235 



Reproductive cells, 77-12$ passim ; in 

 relation to the "body," 241 



Reptiles, amatory emotions of, 245 



Richarz, theory of sex, 32 



Rhinoderma, 234 



Rhythms of life, 208, 209 



Rolph on sex characters, 21 ; on sex 

 in wasps, 38, 39 ; on crustaceans, 41 ; 

 theory of sex, 11 1 ; on sex-cells, 118, 

 125; on fertilization, 150, 151; on 

 parthenogenesis, 168, 169 



Romanes on cuckoo, 254 ; on physio- 

 logical selection, 282, 283 



Rotifers, sexes of, 17; parthenogene- 

 sis in, 162 ; male, 238 



Sabatier, theory of polarities, 100 

 Sacrifice, 285 



Sachs, origin of fertilization, 143 ; na- 

 ture of fertilization, 150 

 Sadler on determination of sex, 29 

 Salensky on primitive Metazoa, 285 

 Schizogenes, multiplication of, 215 

 Schlechter on sex in horses, 43 

 Schleiden, 81 



Schultze, hypothesis of male and fe- 

 male ova, 29 

 Schwann, 82 

 Sea-anemones, asexual multiplication, 



175 

 Sea-cucumber and offspring, 251 



Sea-horse, parental care of male, 234, 



235 

 Secondary sexual characters, 3-7, 18-21 



Self-fertilization, jp 



Seminal vesicles, 223 



Sex, determination of, 27-48 ; theory 

 of, 111-126; origin of, 118, 119 



Sexes, characters of, 14-21 ; different 

 habits, 14-16; sizes of, 16-18; intel- 

 lectual and emotional differences, 

 247-250 



Sex elements, 77-91 ; early separation 

 of, 86 ; compared with Protozoa, 

 112 



Sexual attraction, 246-247 



Sexual maturation, 223-225 



Sexual organs and tissues, 51-57 



Sexual reproduction, 129-145 



Sexual selection, 7-12, 282 



Sexual union, 226-229 



Siebold, Von, experiments on wasps, 

 38, 39; parthenogenesis, 159 



Silkmoth, parthenogenesis of, 158 



Simon on fertilization, 150 



Siphonophora, 180 



Snail, reproductive specialization in 

 the, 56 



Spencer, theory of growth, 204-207 ; 

 laws of multiplication, 262-267 ; pop- 

 ulation question, 266-269 ! factors of 

 evolution, 279 



Spermatogenesis, theory of, 107 



Spermatozoon, 103-109 ; discovery of, 

 103 ; structure, 103, 104 ; forms, 105 ; 

 physiology of, 105 ; resemblance to 

 pollen, 108 ; chemistry of, 108, 109 ; 

 influence of, 277 



Spiculum amoris, 56 



Sponge, reproductive cells, 52, 53 ; 

 hermaphroditism, 66; asexual re- 

 production, 175, 176, 178, 179; alter- 

 nation of generations in Spongilla, 



193 

 Spores, 190-198 

 Sprengel on fertilization in flowers, 



130 

 Starfish, reproduction of parts, 182 

 Starkweather's law of sex, 31, 32 

 Statistics on male and female births, 



30 



Steenstrup on alternation of genera- 

 tions, 185 



Stickleback, habits of, 20; secretion 

 of, 231, 232 



Sterility, 274 



Strasburger on fertilization, 149, 150; 

 on parthenogenesis, 169 



Summer eggs, 162, 163 



