Factors, new, 88 loss of, 96 Factorial representation of varieties, 158,165 Falcons, geographical races, 147 Fasciation, 49 Ferments, Boyle on, 54 Finger-prints of twins, 44 Fixity and Variability in species, 25 Flax, climatic experiments, 197 Fowl, Silky, 84 Leghorn, 85,90 Dominant white, 94 Wyandotte, 97 Rumpless, 46 Foxes, incompatibility with dogs, 241 Free-martin, 44 Fringillidae, sterility of hybrid, 241 Fundulus, cyclopian, 50 Gallus, invariability of wild species, 13 and origin of poultry, 90,97 Genitalia, a basis for classification in insects, 13 Gentians, climatic experiments, 197 Geometrical structure and differentiation, 54,56 Geometrical distinction between germ-cells and somatic cells, 58 Gladiolus, right and left, 57 Gnophus obscurata, protective colouring, 141 Goldfinch, geographical races, 147 Gonioctena variabilis, variation in sexes of, 121 Gouldian Finch, polymorphism, 148,149 Gracilaria stigmatella, experiments on, 193 Grantia, large varieties of, 125 Ground-Squirrels, local forms of, 132 Grouse, red, variation, 29 Guillemot, Ringed, 150 Guinea-pig, Brown-Séquard's experiments on, 198 Gynandromorphs, 45