. Biology . wdth theresult that all peas are of one color, in this case, yellow. Theprinciple of dominance, where two factors for the same characterlie together in the fertilized egg, was thus recognized. Thesame reasoning is applied in respect to all other characteristicsof the adult organisms. Mendels experiments were carried out long before the essen-tial features of maturation were known; never<;hele5s he sug-gested that some process must take place during the formation 222 THE PERPETUATION OF ADAPTATIONS of the hybrid germ cells, whereby the yellow and green factorsare separated from o
. Biology . wdth theresult that all peas are of one color, in this case, yellow. Theprinciple of dominance, where two factors for the same characterlie together in the fertilized egg, was thus recognized. Thesame reasoning is applied in respect to all other characteristicsof the adult organisms. Mendels experiments were carried out long before the essen-tial features of maturation were known; never<;hele5s he sug-gested that some process must take place during the formation 222 THE PERPETUATION OF ADAPTATIONS of the hybrid germ cells, whereby the yellow and green factorsare separated from one another, so as to produce germ cellshaving only one factor for green or for yellow. This is known asMendels principle of segregation. The hybrid ovule containingboth factors is said to be heterozygous, and the two factors forthe same character (here color) are called allelomorphs, one ofwhich is dominant, the other recessive. If only one type offactors is present in an ovule, it is said to be Fig. 05.—Example of IVIendelian inheritance in which the hybrid (Fi) isintermediate between the two parents, but showing segregation of the two factorsin the germ cells giving in the F2 generation the proportion of i : 2 : i. The crossis made between white and red races of Mirabilis jalapa (the four oclock).The hybrid (Fi) is pink, and these when inbred give white, pink, and red flowersin the proportion of i : 2 : i (F2). (From Morgan.) Now if the hybrid plants are self-fertilized, , through unionof their own germ cells, and if segregation of factors occurs dur-ing the formation of these germ cells in both anthers and ovules,then the following combinations may occur (Fig. 94). Thegreen-bearing anther may unite with a green-bearing ovule,and the result is green (homozygous); or a green-bearing anther MENDELIAN INHERITANCE 223 may unite with a yellow-bearing ovule, and the result is aheterozygous yellow, since yellow is dominant. Or a yellow-bearing anther may unite wit
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