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652

* Insects, relative size of the cerebral gauglia in, 54; male, appearance of, before the females, 212; pursuit of female, by the males, 221; period of development of sexual characters in, 236; secondary sexual characters of, 274; stridulation, 566.
 * Insessores, vocal organs of, 370.
 * Instep, depth of, in soldiers and sailors, 32.
 * Instinct and intelligence, 67.
 * , migratory, vanquishing the maternal, 107, 113.
 * Instinctive actions, the result of inheritance, 105.
 * impulses, difference of the force of, 110, 111; and moral impulses, alliance of, 110.
 * Instincts, 66; complex origin of, through natural selection, 67; possible origin of some, 67; acquired, of domestic animals, 104; variability of the force of, 107; difference of force between the social and other, 111, 126; utilised for new purposes, 571.
 * Instrumental music of birds, 375, 378.
 * Intellect, influence of, in natural selection in civilised society, 136.
 * Intellectual faculties, their influence on natural selection in man, 127; probably perfected through natural selection, 128.
 * Intelligence, Mr. H. Spencer on the dawn of, 67.
 * Intemperance, no reproach among savages, 119; its destructiveness, 137.
 * Intoxication in monkeys, 7.
 * Iphias glaucippe, 313.
 * Iris, sexual difference in the colour of the, in birds, 383, 425.
 * Ischio-public muscle, 41.
 * Ithajinis cruentus, number of spurs in, 364.
 * Iulus, tarsal suckers of the males of, 274.


 * Jackals learning from dogs to bark, 73.
 * Jack-snipe, coloration of the, 491
 * Jacquinot, on the number of species of man, 174.
 * Jaeger, Dr., length of bones increased from carrying weights, 32; on the difficulty of approaching herds of wild animals, 100; male Silver-pheasant, rejected when his plumage was spoilt, 419.
 * Jaguars, black, 539.
 * Janson, E. W., on the proportions of the sexes in Tomicus villosus, 253; on stridulant beetles, 302.
 * Japan, encouragement of licentiousness in, 46.
 * Japanese, general beardlessness of the, 560; aversion of the, to whiskers, 581.
 * Jardine, Sir W., on the Argus pheasant, 384, 403.
 * Jarrold, Dr., on modifications of the skull induced by unnatural position, 56.
 * Jarves, Mr., on infanticide in the Sandwich Islands, 257.
 * Javans, relative height of the sexes of, 559; notions of female beauty, 580.
 * Jaw, influence of the muscles of the, upon the physiognomy of the apes, 54.
 * Jaws, smaller proportionately to the extremities, 33; influence of food upon the size of, 33; diminution of, in man, 53; in man, reduced by correlation, 562.
 * Jay, young of the, 481; Canada, young of the, 481.
 * Jays, new mates found by, 407; distinguishing persons, 412.
 * Jeffreys, J. Gwyn, on the form of the shell in the sexes of the Gasteropoda, 262; on the influence of light upon the colours of shells, 263.
 * Jelly-fish, bright colours of some, 260.
 * Jenner, Dr., on the voice of the rook, 375; on the finding of new mates by magpies, 407; on retardation of the generative functions in birds, 409.
 * Jenyns, L., on the desertion of their young by swallows, 108; on male birds singing after the proper season, 409.
 * Jerdon, Dr., on birds dreaming, 74; on the pugnacity of the male bulbul, 360; on the pugnacity of the male Ortygornis gularis, 363; on the spurs of Galloperdix, 364; on