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frequency of white plumage in, 493; vocal courtship of, 567; naked skin of the head and neck in, 601.
 * Birgus latro, habits of, 270.
 * Birkbeck, Mr., on the finding of new mates by golden eagles, 408.
 * Birthplace of man, 155.
 * Births, numerical proportions of the sexes in, in animals and man, 215, 216; male and female, numerical proportion of, in England, 242.
 * Bischoff, Prof., on the agreement between the brains of man and of the orang, 6; figure of the embryo of the dog, 10; on the convolutions of the brain in the human fœtus, 11; on the difference between the skulls of man and the quadrumana, 149; resemblance between the ape's and man's, 200.
 * Bishop, J., on the vocal organs of frogs, 350; on the vocal organs of corvine birds, 370; on the trachea of the Merganser, 374.
 * Bison, American, co-operation of, 101; mane of the male, 521.
 * Bitterns, dwarf, coloration of the sexes of, 461.
 * Biziura lobata, musky odour of the male, 359; large size of male, 362.
 * Blackbird, sexual differences in the, 219; proportion of the sexes in the, 248; acquisition of a song by, 370; colour of the beak in the sexes of the, 383, 491; pairing with a thrush, 414; colours and nidification of the, 455; young of the, 487; sexual difference in coloration of the, 491.
 * Black-buck, Indian, sexual difference in the colour of the, 535.
 * Blackcap, arrival of the male, before the female, 212; young of the, 487.
 * Black-cock, polygamous, 219; proportion of the sexes in the, 248; pugnacity and love-dance of the, 363; call of the, 375; moulting of the, 392; duration of the courtship of the, 405; and pheasant, hybrids of, 414; sexual difference in coloration of the, 491; crimson eye-cere of the, 491.
 * Blacklock, Dr., on music, 572.
 * Black-grouse, characters of young, 465, 471.
 * Blackwall, J., on the speaking of the magpie, 90; on the desertion of their young by swallows, 108; on the superior activity of male spiders, 221; on the proportion of the sexes in spiders, 254; on sexual variation of colour in spiders, 272; on male spiders, 272.
 * Bladder-nose Seal, hood of the, 528.
 * Blaine, on the affections of dogs, 523.
 * Blair, Dr., on the relative liability of Europeans to yellow fever, 194.
 * Blake, C. C., on the jaw from La Naulette, 40.
 * Blakiston, Capt., on the American snipe, 377; on the dances of Tetrao phasianellus, 381.
 * Blasius, Dr., on the species of European birds, 422.
 * Bledius taurus, hornlike processes of male, 299.
 * Bleeding, tendency to profuse, 237.
 * Blenkiron, Mr., on sexual preference in horses, 524.
 * Blennies, crest developed on the head of male, during the breeding season, 338.
 * Blethisa multipunctata, stridulation of, 302.
 * Bloch, on the proportions of the sexes in fishes, 249.
 * Blood, arterial, red colour of, 261.
 * pheasant, number of spurs in, 364.
 * Bluebreast, red-throated, sexual differences of the, 472.
 * Blumenbach, on Man, 28; on the large size of the nasal cavities in American aborigines, 34; on the position of man, 149; on the number of species of man, 174.
 * Blyth, E., on the structure of the hand in the species of Hylobates, 51; observations on Indian crows, 102; on the development of the horns in the Koodoo and Eland antelopes, 234; on the pugnacity of the males of Gallinula cristata, 360; on the presence of spurs in the female Euplocamus erythrophthalmus, 364; on the pugnacity of the amadavat, 366; on the spoonbill, 374; on the