INDEX 389 



Saliva, secretion of, 96. 



Salivary glands, metabolism of, 96. 



Salivary secretion, not a purely mechanistic process, 112. 



Sea, not really rich in life, 306. 



Sea-urchin gastrula, 170. 



Secretion described mechanistically, 98. 



Secretion, psychical, 99. 



Segmentation of the ovum, 129. 



Selection, natural, 228 ; 



from fluctuating variations, 189 ; from mutations, 190. 



Semon, mnemic hypothesis of heredity, 181. 



Senescence, 175. 



Sensation, 2 ; 



analysis of, 13. 



Sense-receptors and the idea of matter, 352. 



Sensori-motor system, 270 ; 



dominant in animals, 271, 273 ; specialisation of, 271, 273 ; essentially 

 the same in all animals, 294 ; absent in plants, 269 ; vestigial in some 

 parasites, 



Sexuality, 174. 



Siphonophores, regeneration in, 163. 



Size of animals, 274. 



Skeleton of vertebrates, 276 ; 

 of arthropods, 276 ; 

 and mobility, 276. 



Soddy, and chemical energy, 361. 



Soma, 179 ; 



evolution of, 223. 



Space, form of, 18 ; 



3 -dimensional, 18; 3-dimensional space an intuition, 19; 2-dimensional, 

 19 ; the form of, depends on modes of activity, 21, 25. 



Species, are categories of structure, 201 ; 



comparison with Platonic ideas, 204 ; criteria of, 202 ; elementary, 193; 

 are intellectual constructions, 203 ; individuality of, 203 ; Linnean, 201, 

 289 ; are phases in an evolutionary flux, 206 ; are families in the human 

 sense, 208 ; systematic, 201. 



Specific organisation, stability of, 186. 



Stahl, and the phlogistic hypothesis, 126 ; 

 and vitalism, 126. 



Stimuli, elemental, 151 ; 



physico-chemical, 151 ; formative, 176 ; complex auditory, 152 ; integra- 

 tion of, 152; individualised, 152, 270; contractile, 103. 



Stimulus and response, functionality of, 152. 



Substantia physica, 46, 355. 



Surface tension, 105, 106. 



Suspensoids, 108. 



Sylvius, the organism a chemical mechanism, 125. 



