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Streptolabis hispoides, 93.
STRUGGLE for existence, 28, 33.
Survival of the fittest, law of,

stated, 33; its action in deter-

mining colour, 67.
SWAInson’s circular and quinarian

theory, 45.
SYLVIADÆ, sexual colouring and

nidification of, 245

in different classes of animals,

111; diverse habits of, 156.
SEXUAL SELECTION, 156; its nor-

mal action to develop colour in
both sexes, 247; among birds,

SIDGWICK, Mr. A., on protective

colouring of moths, 62.
SITTA, sexual colouring and nidi-

fication of, 243.
SITTELLA, sexual colouring and

nidification of, 243.
SNAKES, mimicry among, 101.
Song of birds, instinctive or imita-

tive, 220.
SPECIES, law of population of, 28;

abundance or rarity of, depend-
ent on the adaptation to condi-
tions, 33; definition of, 141,
161; the range and constancy
of, 143; extreme variation in,

163, 164.
SPEED of animals, limits of, 292.
Sphecia craboniforme, 90.
Sphecomorpha chalybea, 96.
SPHEGIDÆ, mimicked by flies, 97.
SPIDERS, wliich minic ants, 98;

and flower buds, 99.
Spilosoma menthastri, 88.
STAINTON, Mr., on moths rejected

by turkeys, 78, 88.
STALACHTIS, a genus of Erycinidæ,

the object of mimicry, 84.
Stinging insects generally conspi-

cuously coloured, 72.
STURNIDÆ, sexual colouring and

nidification of, 244.

TACHORNIS phænicobea, 228.
Tachyris hombronii, 172; ithome,

172; lycaste, 172; lyncida, 172;
nephele, 172; nero, 172; zarinda,

TANAGRIDÆ, sexual colouring and

nidification of, 245.
TAPIR, 299.
TELEPHORI, similar colouring of

two sexes, 114.
TEMPERATE and cold climates fa-

vourable to civilization, 318.
THERATES, mimicked by Hetero-

mera, 95.

Thyca descombesi, 172; hyparete,

172; rosenbergii, 172; zebuda,

Tiger, adaptive colouring of, 52.
Times newspaper on Natural Selec-

tion, 296.
Tools, importance of, to man,

TREE FROGS, probable mimicry by,

TRIMEN, Mr., on rank of the Papi-

lionidæ, 136.
TRISTRAM, Rev. H., on colours of

desert animals, 50.

38, 40; inconvenience of using

the term, 161.
VERTEBRATA, mimicry among, 99.
VOICE of man, not explained by

natural selection, 350.
VOLUCELLA, species of mimic bees,

75, 98.

Trochilium tipuliforme, 90.
TROGONIDÆ, sexual colouring and

nidification of, 241.
TROPICAL birds often green, 52.
Tropics, most favourable to pro-

duction of perfect adaptation
among animals, 68; not favour.
able to growth of civilization,


orioles, 104.
TRUTHFULNESS of some savages,

353; not to be explained on

utilitarian hypothesis, 354.
TURDIDÆ, sexual colouring and

nidification of, 245.
Turnix, 115, 251.
TYNDALL, Professor, on origin of

consciousness, 361.

UPUPIDÆ, sexual colouring and

nidification of, 241.
USEFUL and useless variations, 34.
Utility, importance of the prin-

ciple of, 47, 127.

WALSH, Mr., on dimorphism, of

Papilio turnus, 153.
WEAPONS and tools, how they

affect man's progress, 314.
WEEVILS often resemble small

lumps of earth, 58.
Weir, Mr. Jenner, on

a moth
refused by birds, 89; beetles
refused by birds, 93; on cater-
pillars eaten and rejected by

birds, 119
WESTWOOD, Professor, objections

to theory of mimicry, 108.
WHITE colour in domesticated and

wild animals, 66.
Wild and domesticated animals,

essential differences of, 38-41.
WILL really exerts force, 367;

probably the primary source of

force, 368.
Wood, Mr. T. W., on orange-tip

butterfly, 59.
WOODCOCKS and Snipes, protective

colouring of, 53.
WOODPECKERS, why scarce in Eng-

land, 32.

VARIABILITY, simple, 144.
VARIATIONS, useful and useless, 34;

laws of, 143, 266; as influenced
by locality, 166; of size, 168;
universality of, 287-291; are
there limits to, 291; of domestic

dogs, 293 ; of pigeons, 293.
VARIETIES, instability of, supposed

to prove the permanent dis-
tinctness of species, 26; if su-
perior will extirpate original
species, 36; its reversion then
impossible, 37; of domesticated
animals may partially revert,

XANTHIA, autumnal colours of

these moths, 62.

ZEBRAS, 299,

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