386 THE PHILOSOPHY OF BIOLOGY 



Muscular contraction, 104 ; 



metabolism in, 104 ; heat production in, 104. 

 Muscular and nervous organs, 275. 

 Musculature and weight of body, 275. 

 Mutations, 189 ; 



essential nature of, 193; causes of, 200; must be co-ordinated, 231 ; 



physical model of, 192 ; the material for selection, 230. 



Nageli, and autonomy in development, 160. 

 Natural selection, 228 ; 



generality of, 229 ; a slow process, 230. 

 Nebulae, 315. 

 Nebular hypothesis, 296. 

 Nerve impulses, 100 ; 



velocity of, 10 1 ; integration of, 273. 

 Nervous system, 272 ; 



in co-ordination of activities, 171 ; paths in, 157. 

 Nervous activity, 107 ; 



metabolism in, 107 ; electric changes in, 107 ; influence of metabolism 



on, 97. 

 Nothing, a pseudo-idea, 18. 

 Nucleus, evolution of, 222. 



division of, 130, 182. 



Ontogenetic stages, 255. 



Orders of individuality, 171. 



Organism, definition of, 331 ; 



analysis of its activities, 109 ; animal and plant, 76 ; considered energet- 

 ically, 77; the dominant, 258; a function of the environment, 216; 

 a mechanism, 51 ; the primitive, 222; a physico-chemical system, 65 ; 

 a thermodynamic mechanism, 104. 



Organic chemical syntheses, 317. 



Organisation in development, 137. 



Organ-rudiments, 257. 



Osmosis, 95, 99. 



Ostracoderms, 291. 



Ostwald on catalysis, 91. 



Ovum, development of, 129 ; 



maturation of, 198, 239 ; an intensive manifoldness, 302 



Oxidases, 105. 



Oxygen in metabolism, 69. 



Pain, Bergson on, 281. 

 Palaeontology, 210 ; 



relates groups of organisms, 211. 



