i. 160;

origin of, in man, i. 161.

SOLDIERS, American, measurements of, i. 114.

SOLDIERS and sailors, difference in the proportions of, i. 116.

_Solenostoma_, bright colours and marsupial sack of the females of, ii. 22.

SONG of male birds appreciated by their females, i. 63; want of, in brilliant plumaged birds, ii. 94; of birds, ii. 163.

_Sorex_, odour of, ii. 279.

SOUNDS admired alike by man and animals, i. 64; produced by fishes, ii. 23; produced by male frogs and toads, ii. 27; instrumentally produced by birds, ii. 63 _et seqq._

SPAIN, decadence of, i. 178.

_Sparassus smaragdulus_, difference of colour in the sexes of, i. 337, 338.

SPARROW, pugnacity of the male, ii. 40; acquisition of the Linnet's song by a, ii. 55; coloration of the, ii. 198; immature plumage of the, ii. 188.

SPARROW, white-crowned, young of the, ii. 217.

SPARROWS, house- and tree-, ii. 170.

SPARROWS, new mates found by, ii. 105.

SPARROWS, sexes and young of, ii. 212; learning to sing, ii. 334.

_Spathura Underwoodi_, ii. 77.

SPAWNING of fishes, ii. 15, 19.

SPEAR, origin of the, i. 234.

SPECIES, causes of the advancement of, i. 172; distinctive characters of, i. 214; or races of man, i. 217; sterility and fertility of, when crossed, i. 122; supposed, of man, i. 226; gradation of, i. 227; difficulty of defining, i. 228; representative, of birds, ii. 190, 191; of birds, comparative differences between the sexes of distinct, ii. 192.

SPECTRE-INSECTS, mimickry of leaves by, i. 414.

_Spectrum femoratum_, difference of colour in the sexes of, i. 361.

SPEECH, connection between the brain and the faculty of, i. 58.

"SPEL" of the black-cock, ii. 60.

SPENCER, Herbert, on the dawn of intelligence, i. 37; on the origin of the belief in spiritual agencies, i. 66; on the origin of the moral sense, i. 101; on the influence of food on the size of the jaws, i. 118; on the ratio between individuation and genesis, i. 318; on music, ii. 336.

SPERM-WHALES, battles of male, ii. 240.

SPHINGIDAE, coloration of the, i. 396.

SPHINX, Humming-bird, i. 399.

_Sphinx_, Mr. Bates on the caterpillar of a, i. 416.

SPIDERS, i. 337; male, more active than female, i. 272; proportion of the sexes in, i. 314; male, small size of, i. 338.

_Spilosoma menthrasti_, rejected by turkeys, i. 398.

SPINE, alteration of, to suit the erect attitude of man, i. 143.

SPIRITS, fondness of monkeys for, i. 12.

SPIRITUAL agencies, belief in, almost universal, i. 65.

SPOONBILL, ii. 60; Chinese, change of plumage in, ii. 179.

SPOTS, retained throughout groups of birds, ii. 131; disappearance of, in adult mammals, ii. 303.

SPRENGEL, C. K., on the sexuality of plants, i. 260.

SPRING-BOC, horns of the, ii. 251.

SPROAT, Mr., on the extinction of savages in Vancouver Island,