i. 263, 265;

male and female, numerical proportion of, in England, i. 300.

BISCHOFF, Prof., on the agreement between the brains of man and of the Orang, i. 11; figure of the embryo of the dog, i. 15; on the convolutions of the brain in the human foetus, i. 16; on the difference between the skulls of man and the quadrumana, i. 190.

BISHOP, J., on the vocal organs of frogs, ii. 28; on the vocal organs of corvine birds, ii. 55; on the trachea of the _Merganser_, ii. 60.

BISON, American, mane of the male, ii. 267.

BITTERNS, dwarf, coloration of the sexes of, ii. 179.

_Biziura lobata_, musky odour of the male, ii. 38; large size of male, ii. 43.

BLACKBIRD, sexual differences in the, i. 268; proportion of the sexes in the, i. 307; acquisition of a song by a, ii. 55; colour of the beak in the sexes of the, ii. 72, 227; pairing with a thrush, ii. 113; colours and nidification of the, ii. 170; young of the, ii. 219; sexual difference in coloration of the, ii. 226.

BLACK-BUCK, Indian, sexual difference in the colour of the, ii. 288.

BLACKCAP, arrival of the male, before the female, i. 259; young of the, ii. 219.

BLACK-COCK, polygamous, i. 269; proportion of the sexes in the, i. 306; pugnacity and love-dance of the, ii. 45; call of the, ii. 60; moulting of the, ii. 83; duration of the courtship of the, ii. 100; sexual difference in coloration of the, ii. 226; crimson eye-cere of the, ii. 227; and pheasant, hybrids of, ii. 113.

BLACK-GROUSE, characters of young, ii. 185, 194.

BLACKWALL, J., on the speaking of the magpie, i. 59; on the desertion of their young by swallows, i. 84; on the superior activity of male spiders, i. 272; on the proportion of the sexes in spiders, i. 314; on sexual variation of colour in spiders, i. 337; on male spiders, i. 338.

BLADDER-NOSE Seal, hood of the, ii. 278.

BLAINE, on the affections of dogs, ii. 270.

BLAIR, Dr., on the relative liability of Europeans to yellow fever, i. 243.

BLAKE, C. C., on the jaw from La Naulette, i. 126.

BLAKISTON, Capt., on the American snipe, ii. 64; on the dances of _Tetrao phasianellus_, ii. 69.

BLASIUS, Dr., on the species of European birds, ii. 124.

_Bledius taurus_, hornlike processes of male, i. 374.

BLEEDING, tendency to profuse, i. 292.

BLENKIRON, Mr., on sexual preference in horses, ii. 272.

BLENNIES, crest developed on the head of male, during the breeding season, ii. 12.

_Blethisa multipunctata_, stridulation of, i. 379.

BLOCH, on the proportions of the sexes in Fishes, i. 308.

BLOOD, arterial, red colour of, i. 323.

BLOOD-PHEASANT, number of spurs in, ii. 46.

BLUEBREAST, red-throated, sexual differences of the, ii. 195.

BLUMENBACH, on Man, i. 111; on the large size of the nasal cavities in American aborigines,