INDEX. 



321 



Protomyxa, 150 



Protoplasm, metabolism of, 86, Sy, 

 122, 123; in fertilisation, 159, 

 160 ; mechanics of, 223 ; in rela- 

 tion to cell-division, 223, 224 



Protozoa contrasted with Metazoa, 

 57, 88, 89 ; illustrating cell- 

 phases, II9-121; conjugation of, 

 148-15 1 ; asexual multiplication, 

 192 ; immortality of, 90, 166, 

 258, 261 ; alternation of genera- 

 tions in, 208 



Puberty, 241, 242 



Purkinje, 86 



Pycnogonid, male with young, 273 



Rate of increase, 283, 284 



Rate of reproduction, 283-289 



Rauber on somatic and reproduc- 

 tive cells, 93 



Regeneration, 189, 190 



Reproduction, processes of, 137- 

 217; theory of, 221-263; origin 

 of, 232, 233 ; in relation to en- 

 vironment, 234-236 ; nemesis of, 

 234, 255 



Reproductive cells, Si -1^2 passim ; 

 in relation to the "body," 261 



Reptiles, amatory emotions of, 

 265, 266 



Richarz, theory of sex, 37 



Rhinoderma, 254 



Rhythms of life, 224, 225 



Rolph on sex characters, 25 ; on sex 

 in wasps, 44 ; on crustaceans, 46 ; 

 theory of sex, 117 ; on sex-cells, 

 125, 133 ; on fertilisation, 160, 

 161 ; on parthenogenesis, 1 81 



Romanes on cuckoo, 275 ; on 

 physiological selection, 307, 308 



Rotifers, sexes of, 20 ; partheno- 

 genesis in, 174; male, 257 



Sabatier, theory of polarities, 106 



Sacrifice, 311 



Sachs, origin of fertilisation, 153; 



nature of fertilisation, 160 

 Sadler on determination of sex, 34 

 Salensky on primitive Metazoa, 311 

 Schizogenes, multiplication of, 232 

 Schlechter on sex in horses, 49 

 Schleiden, 86 



Schultze, hypothesis of male and 

 female ova, 34 



Schwann, 86 



Sea-anemones, asexual multiplica- 

 tion, 188, 189 



Sea-cucumber and offspring, 272 



Sea-horse, parental care of male, 

 254,255 



Secondary sexual characters, 3-8, 

 22-24 



Self-fertilisation, 73 



Seminal vesicles, 241 



Sex, determination of, 32-54 ; 

 theory of, 117-133; origin of, 

 126 



Sexes, characters of, 16-25; different 

 habits, 16-19; sizes of, 19-22; 

 intellectual and emotional differ- 

 ences, 267-271 



Sex elements, 81-95 ? early separa- 

 tion of, 91 ; compared with Pro- 

 tozoa, 119 



Sexual attraction, 266, 267 



Sexual maturation, 241, 242 



Sexual organs and tissues, 57-63 



Sexual reproduction, 137-159 



Sexual selection, 8-14, 307 



Sexual union, 245-247 



Siebold, Von, experiments on wasps, 

 44, parthenogenesis, 170 



Silkmoth, parthenogenesis of, 169 



Simon on fertilisation, 161 



Siphonophora, 194 



Snail, reproductive specialisation in 

 the, 62 



Spencer, theory of growth, 220-224 ; 

 laws of multiplication, 284-289 ; 

 population question, 288-292 ; 

 factors of evolution, 304 



Spermatogenesis, theory of, 113 



Spermatozoon, 109-115; discovery 

 of, 109; structure, 1 10 ; forms, 

 III; physiology of, in ; resem- 

 blance to pollen, 114; chemistry 

 of, 115 ; influence of, 301 



Spiculum amoris, 62 



Sponge, reproductive cells, 58, 59 ; 

 hermaphroditism, 70 ; asexual 

 reproduction, 188, 189, 192, 193 ; 

 alternation of generations in Spon- 

 gilla, 208, 209 



Spores, 205-214 



