s, 87;
alterations made by, 87.

Rocks, crystalline or plutonic:
sedimentary, 85;
eruptive, 88;
new, 59;
of Grand Canon, 90;
testimony of, establishes evolution, 100.

Salamanders, 45, 46.

Salts, of sodium, chlorine, magnesium, potassium, 24.

Samoan Islands, 103.

Sandstone, 90.

Science, what is it? 5, 6;
physiological, 14.

Sea anemones, 68.

Sea elephant, 38.

Seals, 38, 39, 40, 209.

Selection,
natural, doctrine of, 116, 117, 118;
struggle for existence, 124, 125;
simply trial and error, 131, 136,
artificial, 136, 137, 138;
laws of, in mental phenomena, 203.

Sequence, physiological, in training animals, 209; 210.

Series,
sedimentary, 84, 90, 92;
crystalline or plutonic, 85;
Azoic or Archaean, age of, 92.

Shale, 89.

Shark,
common, most fundamental form, 46;
embryo of, hammerhead;
embryos of, 66.

Sheep, 157.

Simiidae, 160, 163.

Skate, embryos of, 66.

Snails, 45;
shells of, 95;
land snails, 103;
Hawaiian and Polynesian, 104.

Society Islands, 103.

Solar system, origin of, 84.

Solomon Islands, 103.

Species, origin of human, 153.

Spencer, Herbert, 8.

Squirrels,
evolved from terrestrial rodents, 14; 41;
flying, true rodents, 41.

Starch, 24.

Stephenson, 10.

Strata, 88, 89;
arranged according to ages, 89; 90;
time of formation, 92.

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,