Origins of Mendelism / Robert C. Olby, with an introduction by Professor C. D. Darlington.

  • Olby, Robert C. (Robert Cecil), 1933-
Date:
1966
Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: Origins of Mendelism / Robert C. Olby, with an introduction by Professor C. D. Darlington. Source: Wellcome Collection.

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    I yo Appendix species. The same combination taking place between a pollen grain and an ovule both segregated in the sense of the mother of the hybrid, the product will revert by itself into the species of the latter. On the other hand, if the combination takes place between a pollen grain and an ovule both segregated in opposite senses, a true cross fertilisation is brought about, like that which gave birth to the hybrid itself, and the result will be a form still inter¬ mediate between the two specific types. The fertilisation of an ovule not segregated, by a pollen grain segregated in one sense or the other would give a quarteron [i.e. a back-crossed hybrid, see Table II, p. 68] ; and since segre¬ gations can take place in all degrees as much in the poUen as in the ovules, combinations will arise which chance alone directs. These would give rise to that multitude of forms which we have seen produced in the l^inaria hybrids and in Vetunia^ from the second generation on¬ wards. Naudin, C. 1863. Nouvelles recherches sur l'hybridité dans les végétaux. Ann. Sci. Nat. Botanique, sér. 4, 191-194. Galton : Stability of Туре I wül now explain what I presume ought to be under¬ stood, when we speak of the stability of types, and what is the nature of the changes through which one type yields to another. Stability is a word taken from the language of mechanics; it is felt to be an apt word; let us see what the conception of types would be, when applied to mechanical conditions. It is shown by Mr. Darwin, in his great theory of The Origin of Species^ that all forms of or¬ ganic life are in some sense convertible into one another, for all have, according to his views, sprung from common ancestry, and therefore A and В have both descended from C, the lines of descent might be remounted from A to C, and redescended from С to B. Yet the changes