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Gates obtained a single plant among offspring of rubrinervis in which the sepals were red throughout, and to this he gave the name rubricalyx. When selfed this plant gave rise to both rubricalyx and rubrinervis, and in the second generation when the rubricalyx was selfed again the numbers of the two were approximately 3 to 1.
It is claimed by mutationists that mutations are not new combinations or separations of Mendelian unit characters already present, but are themselves new characters, though not always necessarily, as in the case of rubricalyx, new unit characters in the Mendelian sense.
Rubricalyx is therefore a dominant heterozygote, and this fact was further confirmed in the third generation when a selfed plant gave 200 offspring all rubricalyx, the mother plant having evidently been homozygous for the red character.
The question to be considered here is how far the claim is justified that the facts of this kind hitherto discovered afford an explanation of the process of evolution. It seems probable that mutations are of different kinds, as exemplified in Oenothera by gigas and rubricalyx respectively, the former producing only sterile hybrids, the latter behaving exactly like a Mendelian unit.
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