Factors, origin of Feathers, evolution of Flat-fishes, mutations of Flight, evolution of Flounder Foa, on lactation; on grafting ovaries Foges Fowls, castration of; origin of breeds Fractionation of Mendelian factors Fränkel Frog, thumb-pad _Gallus bankiva_ Gates, Dr. R. Ruggles Geddes and Thomson Gemmules Genital ducts _Gigas, Oenothera_ _Gillichthys Gipsy moth Goltz and Ewald Gonads, hormones of Goodale, H. D. Grafting, of ovaries or testes Graves' disease Gudernatsch Guthrie, C. C. Gynandromorphism Haemophilia Hanau Hegner Herdwick sheep, castration in Heredity; and sex Hermaphroditism Hill, J. P. Horns Houssaye _Inachus scorpio_ Insects, heredity of sex in Interstitial cells Intromittent organs Japanese long-tailed fowls; artificial treatment of Kammerer Kellog Kopec Lactation, dependence on stimulation, in males; regulation of _Laevifolia, Oenothera_ Lamarck Lamarckian theory Lane-Claypon, Miss; and Starling, on ovaries of rabbit Larvae of insects _Lata, Cenothera_ Leghorn, White Lemon-dab Leopold and Ravana Lepidoptera, castration in _Leptinotarsa_ _Limantria dispar_ Limon Linnæus Lode Loeb, on "blind fish; on blindness in cave animals; on tadpoles and thyroid Lop-eared rabbits, grafting experiments Lotsy, Professor; on crossing Lutein, of corpora lutes Male characters in female Mallard crosses Mammary glands; origin of rudimentary in male Marshall; and Jolly Marsupials, relation of foetus to pouch; scrotum of Masked crab Meisenheimer; thumb-pad of frog _Mendel's Principles of Heredity_ Mendelism; and castration Menstruation Metamorphosis; in Flat-fishes; causes of; and hormones; and diagnostic characters Michaux, Midwife toad, Milk glands, Mole, eyes of, Monotremata, origin of milk glands, Morgan, T. H., on blindness in cave animals, on mutations, on sex:, on sex-linked heredity, on sexual dimorphism in _Drosophila_, on variation, Mutations, in antlers, Natural selection, Nuptial plumage, Nussbaum, _Nyssia zonaria_ O'Donoghue, development of milk glands, _OEnothera_, mutations, _grandiflora_, lata_, _Lamarckiana_, Onagra, species of, _Origin of Species_, Darwin's, _Ornithorhyncus_, corpus luteum Orthogenesis, Otariidae, scrotum, Ovaries, position of, Ovary, in birds, Ovulation, Pangenesis, Parthenogenesis, Parturition, Pearson, Karl, Pheasant, male, gynandramorphism in Phillips, John C., _Philosophie Zoologique_ Phoeidae, testes, _Physiology of Reproduction_, Picotee Sweet Pea, Pigeons, Pigment, absence in cave animals, Pile fowls, Pintail duck, crosses, Plaice, _Pleuronectes flesus_, _glacialis_, _platesca_, Plymouth Rock fowl, Pole-dab, Poll, Preformation, _Problems of Genetics_, Prong buck, Pro-oestrus, _Proteus_, eyes of, Prototheria, milk glands in,