Heredity, mental and moral, [188]

Heroism, [193], [200], [227]

History, [15]

Hope, [262]

Huxley (quoted), [99], [171], [273]

Hydra, [37]

Insects, [65], [105]

Instinct, [127], [131]

Intellect, [117], [124]

Intelligence, [117]