i. 403;

on mimickry, i. 411; on the caterpillar of a _Sphinx_, i. 416; on the vocal organs of the umbrella-bird, ii. 58; on the toucans, ii. 227; on _Brachyurus calvus_, ii. 309.

BATOKAS, knocking out two upper incisors, ii. 340.

BATRACHIA, ii. 25; eagerness of male, i. 272.

BATS, sexual differences in the colour of, ii. 286.

BATTLE, law of, i. 182; among beetles, i. 375; among birds, ii. 40; among mammals, ii. 239 _et seq._; in man, ii. 323.

BEAK, sexual difference in the forms of the, ii. 39; in the colour of the, ii. 72.

BEAKS, of birds, bright colours of, ii. 227.

BEARD, development of, in man, ii. 317; analogy of the, in man and the quadrumana, ii. 319; variation of the development of the, in different races of men,