Nervous arc, 33; system of higher animals, 297 Nest-building, observations on, 135 NOIRÉ on concept, 167 Norwegian ponies, 109 Nucleus division, 12 O Object and subject, 245, 276 Octopus, intelligence of, 158 _Œcophylla_, behaviour of, 210 Orchids, fertilization of, 29 Organic basis of differentiation of consciousness, 53 Organic behaviour in development, 15 Organic selection, 37 (note), 115 Overproduction of movements, 164 Oxalis, sensitive, behaviour of, 27 _Oxybelus_, mode of carrying prey, 76 P PALEY, definition of instinct, 64 Paramecium, behaviour of, 3, 296 Partridge, note of young, 93 PECKHAM, Dr. G. W., on instinct, 65; on solitary wasps, 72 ff., 126 ff. Pecking instinct of chicks, 93 Peewit, note of young, 93 _Pelopœus_, instincts of, 72 Perceptual stage of mental development, 59 Personality, 245, 257 Pheasants, note of young, 92; inherited co-ordination in, 95; plumage of Argus, 262 _Philanthus_, prey of, 73; mode of stinging prey, 74 Physiological aspect of animal behaviour, 295 Pigeons, nests of, 136 Pigs, wild, behaviour of, 196 Plants, behaviour of, 24 Plastic period of life, 168 Plasticity of tissues, 40; of behaviour, 172 Play of animals, 248 ff.; biological value of, 250; psychological aspect of, 256, 311, 316 PLAYNE, Mr. H. C., on pigeons’ nests, 136 Pleasure, 241; ambiguity in word, 285 _Polistes_, locality studies of, 131 _Pompilus_, mode of carrying prey, 76; Fabre’s observation on, 129 Presentative elements distinguished from re-presentative, 46 Primary instincts (Romanes), 108 Projective stage of mental development, 275; senses, 304 _Pronuba_, instinct of, 82 Propensity, instincts as, 64; congenital, 176 Protoplasm, fundamental properties of, 296 Psychological aspect of play, 256; purpose, 294; aspect of animal behaviour, 315 R Rational process distinguished from intelligent, 59, 138 Reflex action, 31, 35, 298 ff.; relation of instinct to, 70 Relationships, importance of, 202 Re-presentative elements distinguished from presentative, 46 _Rhynchites_, instinct of, 121 ROMANES, G. J., on “discrimination” and “perception” in plants, 32; on instincts of solitary wasps, 73; definition of instinct, 99; on primary and secondary instincts, 108, 109; on ants, 126; on general ideas, 166; on animal communication, 201; on cruelty in cat, 277 ROMANES, Miss, observations on capuchin monkey, 188, 278 Roots of spinal nerves, 299 ROTHNEY, Mr. G. A. G., on Indian ants, 212 S SCHNEIDER, on octopus, 158 SCOTT, Dr. D. H., on fern fertilization, 25 Scratching in duckling, 96 Sea anemone, diffused nervous system of, 32 Secondary instincts (Romanes), 108, 109 Segmental nature of central nervous system, 299