Vigour and heredity / by J. Lewis Bonhote.

  • Bonhote, J. Lewis (John Lewis), 1875-1922.
Date:
1915
Catalogue details

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

Credit: Vigour and heredity / by J. Lewis Bonhote. Source: Wellcome Collection.

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    8 VIGOUR AND HEREDITY It is obvious that if the offspring, F ^ generation, started with the same amount of vigour, and, if they were to breed at that vigour, the initial vigour of the generation would still be the same, and the ids of both the parents would be equally strong, and consequently the characters would be more evenly blended, and the prepotency would not neces¬ sarily be marked in any way. (I am only referring here to the Mendelian heterozygotes ; the pure dominants and ré¬ cessives would of course appear as usual.) Suppose the initial vigour of the father very low and of the mother very high, the initial vigour of the offspring will then be intermediate ; but it is more than possible that, where the difference in vigour between the parents is great, the characters of the parent with weaker vigour are unable to develop,* and have, therefore, to lie latent (though not by any means to necessarily become lost).t This is, I think, a possible explanation of some forms of prepotency, which, as we can see, may therefore be complete or partial. It is, however, more likely to be partial, since, as the vigour of the offspring is intermediate, it is unlikely that all the characters of a parent with a high initial vigour should develop : they may all get a start ahead of those of the weaker parent, but only some will reach their full develop¬ ment. Let us, however, trace the case a little further; if these offspring be paired at their highest vigour, then their children will have the same initial vigour, and are therefore more likely to resemble their grandmother, since their initial vigour is nearer to hers than to that of their grandfather, but as both the parents' germs start equal in vigour the characters of the grandparents will be more blended, and the prepotency (which in this case does not really exist at all) much less marked. Inbreeding. — Another point to be considered is In¬ breeding, and how this affects vigour and inheritance. Inbreeding is popularly supposed to have two effects— For further details, see Chapter XI. ]■ The action may perhaps be roughly compared to a tree or plant in which the main stem or leader has been cut off—several branches may try and grow, but as a rule one eventually gets the lead and the others remain imdeveloped—they do not die, and are still potentially capable of development, but their development is retarded and crushed owing to the lead gained by the foremost.