Ear, section, |359|. Echinoderms, 184. Economic value of green plants, 117; importance of spawning habits of fishes, 239. Ectoderm, 177. Effect of light on leaves, 88. Efficiency of a week, |370|. Egg, 177, 246. Egg-laying habits of fishes, 238. Ehrlich, Paul, 403. Elasmobranchs, 187. Elements, chemical, 20, |21|. Elodea, |49|, 50. Embryo, 58, 59, |103|; of bird, 247; of mammal, |247|. Emulsion, 306. Endoderm, 177. Endoskeleton, definition, 237. Endosperm, 67. Enemies of forests, 113, |114|. Energy, 64; of a tree, |94|; source of, 88. English sparrow, 212. Environment, |19|, 19; care and improvement of, 26; changes in, 25; determines kind of plants and animals, 23, |23|, |24|; normal, 28; of man, 26, 266; natural, 25; relation to diet, 280; what plants and animals take from, 21. Enzymes, 68, 101, 298. Epicotyl, 59. Epidermis, 86. Epithelial layer, 308. Epithelium, 179. Erosion, prevention of, |106|, 108; at Sayre, Pa., |106|. Essential organs, 36. Esophagus, 302. Eugenics, 261. Eustachian tubes, 300, 359. Euthenics, 264. Evaporation, |99|; of water, 85, 86, |87|. Evolution, 194, 195. Excretion, 181, 270, 332; organs of, 340; in plants, 103. Exercise and circulation, 326; and health, 339. Exoskeleton, 185, 237. Extermination of birds, 211. Eye, compound, |30|; defects in, 361; section of, |360|. Eyestrain, 395. Factory inspection, 379. Fallowing, 82. Fatigue, 326; and nerve cells, |356|. Fats and oils, 60, 273. Fehling's solution, 68, 299. Fermentation, 135, |136|, 150. Fertilization, of fish eggs, |240|; of flower, 54. Fibers, vegetable, 127. Fibrin, 315. Fibrinogen, 315. Fig insect, 43. Filament, 36. Filter beds at Albany, N. Y., |385|. Fins, 233. Fishes, 186; artificial propagation, 240; as food, 201; body of, 232; breathing, 234; circulation, 236, |321|; digestive system, 235; egg-laying habits, 238; food getting, 234; food of, 237; gills, |234|; heart, 236; migration, 238; nervous system, 237; skeleton, 237; senses, 233; swim bladder, 236. Fission, 170. Flagella of bacteria, 142. Flatworms, 183. Flax, |128|. Flea, |225|. Floral envelope, 35. Flower, fertilization of, 54; lengthwise section, |35|; use and structure, 35. Fluid, 181. Fly, a disease carrier, 222; foot of, |223|; life history, |222|; typhoid, 223. Foods, absorption of, 309; adulteration, 288; amphibia as, 202; birds as, 202; cost of, |283|; fish as, 201; fruits and seeds, 119; getting of fish, 234; in cotyledons, 60; inorganic, 274; inspection, 380; is alcohol a food, 289; leaves, 117, |118|; making in green leaf, |93|; mammals as, 202; of animal origin, |279|; of bacteria, 144; of fishes, 237;