Part 31

Struggle for existence, 124; intra-specific, 125; three divisions of, 126-129; 139, 174, 175.

Substances, inorganic, 29.

Sugar, 23, 24.

Survival of the fittest, 129.

Systems, respiratory, excretory, circulatory, 17; organic, reproductive, 18; nervous, 256, 257; blood-vascular, respiratory and excretory, 257; ethical, 286; religious, 288.

Tadpole, 58, 59, 60; larvae, 64.

Tapeworm, a relative of simple worms, 50; 123.

Tapir, 41; Moeritherium, 97.

Thorndike, 209; heredity of mental qualities, 232.

Tidal waves, 85.

Tigers, 101.

Tirawa, 301.

Tissue-cells, 28.

Torga, 183.

Tortoise, soft shelled, of the Mississippi, 45.

Tower, 148.

Transformation, natural, 170.

Tribes, 32.

Tuberculosis, bacillus of, 127.

Turtles, evolution of, 45.

Ungulates, 65.

Uniformitarianism, Lyell's doctrine, 80.

Urea, 29.

Ussher, Archbishop, 178.

Variation, 110; causes of, 111; among individuals, 112, 113; fact of difference, phenomenon of, 114; 115, 118, 119, 121, 129; congenital, 138; human, 174; racial, 177; laws of, in mental phenomena, 203; 232.

Vertebrata, 43.

Vertebrates, backboned animals, fishes the lowest order of, 46; principles of relationship, families, tribes, 47; 53-59; great classes originate together, 64; more complicated, 68; skeleton remains of, succeed invertebrates, 92; testimony of the rocks, 93; largest, 94; appearance of great classes of, 94; 95; classes that make up, 156; lower, arrangement of organs, 201; nervous system of, 256, 257.

Volcanoes, 88.