Hyracotherium, 96.
Ichthyornis, 99.
Ichthyosaurus, 94.
Indians, American, pictography of, 223, 224; of Brazil, 227; life of, 272.
Individual development, a résumé of history of species, 63.
Inertia, 155.
Infant, human, activities of, 216.
Ingestive structures, 17.
Inheritance, 110, 131; biological laws of, 142; paternal and maternal basis of, 144; 145; Mendelian phenomena of, 146; Galton's Law of, 147; laws of, in mental phenomena, 203; strength of, in mental traits, 232; physical, provides mechanism of intellect, 233.
Insects, butterflies, beetles, bees, grasshoppers, spiders, scorpions, 49;
66;
eggs of common house-fly, 67; 82;
nervous mechanism of, 205;
communities of, 207, 258-260, 267;
nervous system of, 256, 257.