Frogs, common, eggs of, 209, 212 growth from the egg, 213-215 English species, 216 European species, 216, 219 green tree-frog of Riviera, 49, 50, 52, 55 method of catching prey, 219 Furniture worm, 351, 352 Gases— oxygen, action of ordinary, 259 experiments as to possible use by athletes, 260-263 Fleuss diving apparatus and diluted supply of, 263-265 ozone, destructive powers of, 253 discoveries of Andrews and Tait with regard to, 252 experiments of Schönbein with regard to, 251, 252 methods of producing, 252, 253, 258 nature of, 252 proportion of, to fresh country or sea-coast air, 253 result of experiments with regard to, 259 signification of name, 252 therapeutic value and uses of, 258, 259 use in water-purification, 256, 258 Geology, Darwin’s discoveries in, 24 table showing history of man in Western Europe, 384 _bis_ Germany, custom of eating preserves with meat in, prevalent, 358 predominance of scientific knowledge in, 8 Gnats, _Anopheles_, malaria germ carried by, 3 _Stegomyia_, yellow fever germs carried by, 2, 3 Gorgas, Colonel, work of, in connection with yellow fever and malaria, 2-5 “Gossamer,” origin of term, 289 Grassi, discovery of the history of the eel by, 70-72 Green-flies, 322 Green tree-frog, 49, 50 Griffin, heraldic, 116 Guinea-pig, native home and original introduction of, 360, 361 various names given to, 360, 361 Halley, Edmund, astronomical discoveries of, 226 date of death, 230 foundation of Royal Society Club by, 230 law of movement of comets discovered by, 226, 230 Milton and, scholars of St. Paul’s School, 228, 229 Newton and, friendship of, 230 Halley’s comet, 226, 230 Hansen, leprosy-bacillus discovered by, 240 Hay fever, individual susceptibility to, 102, 104, 105 probable cause, 105 similarity between vegetable poisonings and, 105 Heart, action of nervous system upon, in man and higher animals, 151 muscular contraction, cause of, 150, 151 rate of beat in higher and lower animals, 152-154 in human species, 151, 152 significance of its beat, 147, 148 valves, action of, 149 Hedge-sparrow, 267 Henslow, Professor, Darwin as influenced by, 36 Herschel, Sir John, definition of word “species” by, 14, 15 Hertwig, Professor, German representative at Darwin Centenary Celebration, 33 Hill, Dr. Leonard, experiments of, with regard to use of oxygen gas, 260-265 Hipparion horse, 84, 85, 86 Hippopotamus age, 380, 386 Histology, origin of, 176 Hook, Robert, _Micrographia_ by, 173, 288, 289 Hooker, Sir Joseph, Darwin and Wallace papers communicated to Linnean Society by, 12, 13 Hop-blight, causes of, 317-319 prevention of, 318, 319 Hop-louse, 317 Hops, brewing industry as affecting growers of, 321 cultivation of, 315-316 curing of, 320 English growers as affected by American and German hop-plantations, 320, 321 uses made of, 315