450 



INDEX 



Factors, and unit characters, 306; 

 complementary, 31.9; cumulative, 

 316, 318; duplicate, 316, 317; lethal, 

 320, 332; multiple, 316; supple- 

 mentary, 319; in existence, 430 



Family, 26 



Faserstrang, 147 



Feathers, 83 



Felis, skull, 391 



Ferns, 24 



Fertilization, 296 



Filial regression, law of, 271, 272 



Fin, pectoral, of dogfish, 75; of 

 Sauripterus, 76; transitional, 76 



Fishes, 37; as vertebrate ancestors, 

 148; in nekton, 215 



Fission, 100 



Flea, amber fossil, 127; jumping 

 adaptations, 220 



Flies, adhesive organs of, 223 



Flight, theories of origin, 154; adapta- 

 tions of bii-ds, 154, 225; in insects, 

 227, 229; in vertebrates, 227-229 



Flippers, 111 



Fly, house, 231 



Flying dragon, 229, 230 



Flying frog, 229 



Flying lemur, 229 



Flying squirrel, 229 



Foetal membranes, ^5, 102; human, 

 46 



Food securing, adaptations, 232; of 

 grazing species, 232; of anteaters, 

 232; of carnivorous animals, 233 



Food supply and climate, 250 



Forelegs, skeletons of, 81 



Fortuitous variations, 268 



Fossils, formation of, 124, 125; inter- 

 pretation of, 127; succession of, 129 



Fossorial ada{)tations, 221 



Fossorial bugs, 254 



Four o'clocks, 281 



Fowls, Andalusian, 281; Sebright 

 bantams, 334; effects of removal 

 of gonads, 334; sex reversal in, 

 335, 336 



Fox, arctic, 242 



Freemartin, 335 



Frog, development of egg, 4U frying, 

 229; sex reversal in, 327; spermato- 

 gonium, 290; spinal ganglion cell, 

 290 



Functions, variations in, 265 



GalApagos islands, 258 

 "Galapagos, Worlds End," 14, 409 

 Galen, 8 



Galeopithecus, 229 

 Galton, 16, 271, 369 

 Galton's laws, 271 

 Gametes, 101; individuality of, 328; 

 of Sphaerella, 326, 327; see Germ 

 cells 

 Gametogenesis, 292, 293 

 Gametophyte, 24 

 Gastrostomus bairdii, 216 

 Gastrula, 40, 41 

 Gastrulation, 42; in frog, 4I; in 



pigeon, 43 

 Gelastocoridae, 254 

 Gemmules, 423 

 Gene, theory of, see Chromosome 



theory 

 Genes, 305; localization of, 310; in 



ontogeny, 322; role of, 432 

 Genetics, 4, 17, 262; foundations of, 



264; practical value, 341 

 "Genetics in Relation to Agricul- 

 ture," 275 

 Genotype, 279 

 Genotypic selection, 353 

 CJenus, 26 



Geographical distribution, 254 ; realms, 

 255, 256; barriers, 257; aids to dis- 

 persal, 258 

 C!eological table, 122 

 Geological time, 120; divisions of, 



122 

 Geology, 119 

 Germ cells, development, 292, 293; 



human, 296; see Gametes 

 Germ plasm, 305; continuity of, 422 

 Germinal continuity, 422 

 Germinal selection, 406 

 Germ layers, 32, 40, 41 

 Gerridae, 254 

 Gibbon, 189 

 Gila monster, 242 

 Gill slits, 37 

 Gipsy moth, 251 

 Girdles, diagram, 77; pelvic, 78; 



pectoral, 79, 80 

 Glands, endocrine, 94; and internal 



environment, 431 

 Gliding, adaptations for, 228 

 Gnathostomata, 147 

 Goddard, 376 



