Morphology, 209; a basis of classification, 210; relates groups of organisms, 211; distinctions of, not absolute, 285, 290; generalised, 250; suggests blood relationships, 213; schemata of, 249, 291; cannot be considered apart from physiology, 285. Mosaic-theory of development, 131. Motion not an intellectual concept, 27; not considered in Euclidean or Cartesian geometry, 26; bodily motion is absolute, 24; outside ourselves is relative, 24. Motor-habits, 38, 155. Multicellular organisms, evolution of, 223. 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. Nägeli, and autonomy in development, 160. Natural selection, 228; generality of, 229; a slow process, 230. Nebulæ, 315. Nebular hypothesis, 296. Nerve impulses, 100; velocity of, 101; 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 energetically, 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. Palæontology, 210; relates groups of organisms, 211. Pangenesis, 181. Paramœcium, division of, 173, 175; responses of, 4. Parasitism, 259; tends to immobility, 290. Parthenogenesis, 176; artificial, 176. Particles, 356. Pecten, eye of, 233. Perception not merely physical stimulation, 7; involves effector activity, 7; involves deliberative action, 9; arises from acting, 50; and choice of response, 155; is unfamiliar cerebral activity, 8; skeletonises consciousness, 40. Peridinians, 77, 163; distribution of, 260. Personal equation, 45. Personality, 167; an intuition, 167; division of, 173; is absolute, 48. Pflüger, and experimental embryology, 131. Phases in physical systems and organic systems, 321; in transforming systems, 308. Phenomenalism, 46.