has reached limit, 85.
in Philadelphia, 63.
introduction, 62.
lives near houses, 70.
nests early, 81.
nests often, 82.
once migratory, 80.
quarrels without animosity, 75.
sociable, 74.
spread of, 65.
stays over winter, 79.
successful, 83.
transported in cars, 67.
unafraid of man, 69.
wintering, 73.

Sparrow, House, 62.

Sphex wasp, 143.

Spider cocoons, 139.

Spider, young, 140.

Spontaneous generation, 159.

Stone lilies, 171.

Story of the horse, 220.

Struggle against enemies, 104.
for food, 91.
for shelter, 92.
for the individual, 90.
for the species, 91, 125.

Sunfish and young, 196.

T

Taste of toad, 118.

Teeth of mammals, 98.

Temperature of mammals, 99.

Tertiary era, 185.

Thayer, concealing color, 115.

Theology and science, 280.

Theology, definition, 280.

Thomas Aquinas and evolution, 12.

Three-toed horse, 227.

Toad, bad taste, 118.
color, 112.
enemies, 113.
short tadpole stage, 112.

Tomato worm, 142.

Turtles and young, 202.

Tusks of elephant, 124.

Tussock worm, 64.

Two methods of reproduction, 194.

Types of insect mouth, 93.

U

Understanding the Bible, 281.

Underwing moth, 130.

V

Variation and natural selection, 49.
by crossing, 53.

Virchow and man's ancestry, 187.

Vireo's color, 115.

W

Wagner and isolation, 241.

Wallace and evolution, 39.

Warm-blooded animals, 99.

Weissman and evolution, 235.

Wilberforce, Bishop, and evolution, 41.

Wintering of ground hog, 103.

Wintering of mammals, 103.

Wintering of squirrels, 103.

Woodchuck, 103.

Woodpecker's nest, 146.

Y

Young growing finer, 272.

APPENDIX

BIBLIOGRAPHY

In connection with each chapter, wherever this is possible, there are
four classes of references. First is named a small and inexpensive but
satisfactory book on the subject. Second, a more comprehensive book,
readily accessible and not unduly expensive. Then a few of the most
satisfactory reference books on the subject independent of cost or
ready availability. Fourth, a list of references to articles in the
eleventh edition of the Encyclopedia Britannica.