INDEX 
Plastic period of life, 168 
Plasticity of tissues, 10; of be- 
haviour, 172 
Play of animals, 248 ff.; biological 
yalue of, 250; psychological as- 
pect of, 256, 311, 316 
Piayne, 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  distin- 
guished from re-presentative, 46 
Primary instincts (Romanes), 108 
Projective stage of mental de- 
velopment, 275; senses, 304 
Pronuba, instinct of, 82 
Propensity, instincts as, 64; con- 
genital, 176 
Protoplasm, fundamental proper- 
ties 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.; rela- 
tion of instinct to, 70 
Relationships, importance of, 202 
Re-presentative elements distin- 
cuished from presentative, 46 
Rhynchites, instinct of, 121 
Romanes, G. J., on “ discrimina- 
tion” and “perception” in 
plants, 32; on instincts of soli- 
tary 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 
Rorsney, Mr. G. A. G., on Indian 
ants, 212 
343 
8 
Scunerper on octopus, 158 . 
Scorr, Dr. D. H., on fern fertiliza- 
tion, 25 
Scratching in duckling, 96 
Sea anemone, diffused nervous 
system of, 32 
Secondary instincts 
108, 109 
Segmental nature of central ner- 
vous system, 299 
Selection, functional, 163; natural, 
shielding of chicks from, 111; 
under uniform and yariable cir- 
cumstances, 175; in playtime of 
life, 319; sexual, 261 ff., 313 
Self, as ideal construction, 239 
Sentience, 62; origin of, 330 
Sexual selection, 261 ff., 313 
Ssarp, Dr. D., on birch-weevil, 
121; on eophylla, 210 
SHELLARD, Mr. E. J., observations 
on staghound, 144 
SHERRINGTON, Prof., on emotion, 
292; on spinal animal, 298 ff. 
Shock effects of physiological, 302 
Srtucox, Miss Edith, quoted, 320 
Sitaris, instincts of, 82 
Slave ants, 215 
Snails, observations on, 157 
Social behaviour, 179; evolution 
of, 225 
Solitary wasps, instincts of, 72 ff. ; 
intelligence of, 126 ff. 
Solomon Islands, rats of, 222 
Sounds emitted by young birds, 
92 
Spatpinc, Douglas, on newly 
hatched turkeys, 49; on in- 
stinct, 99 
Special creation, 297 : 
Speech, connection of, with ra- 
tional process, 58, 233; so-called, 
of monkeys, 198; of children, 
203; aids passage from percep- 
tual to ideational process, 337 
SPENCE on instinct, 63 
Spencer, Mr. Herbert, on instinct 
and reflex action, 70; on play 
due to surplus vigour, 248; on 
pleasure and pain, 284, 287; on 
survival, 288 
(Romanes), 
