Gregor Mendel

It is now clear that the hybrids form seeds having one or other of the two differentiating characters, and of these one-half develop again the hybrid form, while the other half yield plants which remain constant and receive the dominant or the recessive characters in equal numbers.

The course of development consists simply in this; that in each generation the two parental characters appear, separated and unchanged, and there is nothing to indicate that one of them has either inherited or taken over anything from the other.

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 combination of the characters brought together in fertilization.

If A be taken as denoting one of the two constant characters, for instance the dominant, a the recessive, and Aa the hybrid form in which both are conjoined, the expression A + 2Aa + a shows the terms in the series for the progeny of the hybrids of two differentiating characters.

The results of the previously described experiments led to further experiments, the results of which appear fitted to afford some conclusions as regards the composition of the egg and pollen cells of hybrids.

The opinion has been expressed by famous physiologists that the propagation of the hybrids, in so far as they remain fertile, takes place in the same way as in the case of the parental species, and that consequently no fundamental difference is present.

The task of ascertaining the number of different forms under which the offspring of hybrids appear, and of arranging these forms with certainty according to their separate generations, is not an easy one.

It is demonstrated at the outset that no generally applicable law of the formation and development of hybrids has yet been successfully formulated.

The striking regularity with which the same hybrid forms always reappeared whenever fertilization took place between the same species induced further experiments to be undertaken.

The object of the experiment was to observe these variations in the case of each pair of differentiating characters, and to deduce the law according to which they appear in successive generations.

Those who survey the work done in this department will arrive at the conviction that among all the numerous experiments made, not one has been carried out to such an extent and in such a way as to make it possible to determine the number of different forms under which the offspring of hybrids appear, or to arrange these forms with certainty according to their separate generations, or definitely to ascertain their statistical relations.

This seems to be the one correct way of finally reaching a solution to a question whose significance for the evolutionary history of organic forms cannot be underestimated.

The success of the individual experiments was necessarily influenced by the weather, insects, and other external factors.

I know that the results I have obtained will be questioned by many, but I am convinced of their correctness.

My time will come.

The scientific circles to which I have communicated my observations have not yet understood their importance.

I turned to the experiments with peas which are reported here in order to trace the development of hybrids in their progeny.

The characters which were selected for experiment must: 1. Possess constant differentiating characters. 2. The hybrids of such plants must be protected from the influence of foreign pollen during the flowering period.

The various forms of peas selected for crossing showed differences in length and colour of stem, size and form of leaves, position, colour and size of flowers, length of flower stalk, colour, form and size of pods, form and size of seeds, colour of seed-coats and albumen.

Experiments with seed characters lead to the result that the hybrids form seeds which are like one or other of the parental forms, and of these one half yield again the hybrid form, while the other half remains constant with the dominant or recessive character.