Page:Mendel's principles of heredity; a defence.pdf/96

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In precisely similar fashion is the developmental series of hybrids exhibited when three kinds of differentiating characters are conjoined in them. The hybrids form eight various kinds of egg and pollen cells — ABC, ABc, AbC, Abc, aBC, aBc, abC, abc — and each pollen form unites itself again on the average once with each form of egg cell.

The law of combination of different characters which governs the development of the hybrids finds therefore its foundation and explanation in the principle enunciated, that the hybrids produce egg cells and pollen cells which in equal numbers represent all constant forms which result from the combinations of the characters brought together in fertilisation.

It must be the object of further experiments to ascertain whether the law of development discovered for Pisum applies also to the hybrids of other plants. To this end several experiments were recently commenced. Two minor experiments with species of Phaseolus have been completed, and may be here mentioned.

An experiment with Phaseolus vulgaris and Phaseolus nanus gave results in perfect agreement. ''Ph. nanus'' had together with the dwarf axis simply inflated green pods. ''Ph. vulgaris'' had, on the other hand, an axis 10 feet to