. Preventive medicine and hygiene. FiG. 63.—Diagram Showing the Course of Color Heredity in the AndalusianFowl, in Which One Color Does Not Completely Dominate Another. P,parental generation. The offspring of this cross constitute Fi, the first filial or hybridgeneration. F2, the second filial generation. Bottom row, third filial generation.(Kellicott.) ter, however, has not disappeared, for when the black offspring arecrossed together the progeny falls into two groups: some black and somewhite. Three-fourths of the progeny are black; that is, they resemblethe hybrid form and at the same time
. Preventive medicine and hygiene. FiG. 63.—Diagram Showing the Course of Color Heredity in the AndalusianFowl, in Which One Color Does Not Completely Dominate Another. P,parental generation. The offspring of this cross constitute Fi, the first filial or hybridgeneration. F2, the second filial generation. Bottom row, third filial generation.(Kellicott.) ter, however, has not disappeared, for when the black offspring arecrossed together the progeny falls into two groups: some black and somewhite. Three-fourths of the progeny are black; that is, they resemblethe hybrid form and at the same time one of the grandparents, while i. CO coco Fig. 64.—Diagram Showing the Course of Color Heredity in the Guinea-pig, inWhich One Color (Black) Completely Dominates Another (White). Refer-ence letters as in Fig. 63. (Kellicott.) the remaining fourth resemble the other white grandparent. Some ofthese blacks will breed true and are, therefore, known as of the blacks contain a mixture of the black and white charactersand are, therefore, known as heterozygotes. The hereditary transmission 488 HEEEDITY AXD EUGENICS of the color character in these two illustrations through the germ cell isshown in the accompanying diagram. Unit characters may either he positive or negative; that is, they maybe due to the presence or absence of something^ in the germ cell orsperm cell. This something, known as a determiner, is a force, a molec-ular structure or an enzyme (?) in the nuclear matter of the germplasm. Thus, the determiner in the case of pigment is not the pig-ment itself, but something that activates pigment prod
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