INDEX. 



321 



Pi'otomyxa, 150 



Protoplasm, metabolism of, 86, 8y, 

 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, 119-121; 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, 81-132 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, 181 

 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, 31 1 

 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 5 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 



vSpencer, 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, no; 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 



vSpores, 205-214 



