Problems of genetics / by William Bateson.

  • Bateson, William, 1861-1926.
Date:
1913
Catalogue details

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

Credit: Problems of genetics / by William Bateson. Source: Wellcome Collection.

    148/290 (page 126)
    12б PROBLEMS OF GENETICS do well to make himself acquainted with the original from which the following notes are taken. He speaks for example of Helix lapicida. This is on the whole a constant form ranging up to the altitude of 1,300 m., common all over France except at great heights and in the Olive regions where it is restricted to moist places. Though subjected to such diverse conditions it shows only trivial variations in colour and other respects throughout its distribution, excepting that on both sides of the Pyrenees it has a very distinct sporadic variety called Andorrica or microporus. This variety occurs here and there, together with the type-form sometimes in colonies (pp. 26-30 and 86). Bulimus detritus though more restricted in geographical range is a much more variable form. It exhibits great variations in colour, form, and size, and as Coutagne well insists, these are independent of each other. Foreshadowing the methods of factorial analysis he suggests that distinctions in each respect, the modes as he calls them, should be denoted by a letter, or if desired, by a name, and the several combinations of differ¬ ences might thus be most logically and usefully expressed. Of such combinations he says there are at least 18, all of which can be found. The whole possible series does not necessarily occur in the same place, and various localities are characterised by the presence or absence of certain of the combinations as Cou¬ tagne calls them, and by the relative frequency with which they occur. The ideas thus enunciated are much in advance of the ordinary practice of systematists, who give names to forms which are nothing but accidental combinations of factors, just as the horticulturists for practical reasons give names to similar com¬ binations, which as we now know are merely specially noticeable terms in a long series of possibilities. In each case it is rather the factors which should be named than the forms which are constituted by their casual collocation. In this special example of Bulimus detritus the 18 forms are made by the combinations of three pairs of independent factors. Besides these combina¬ tions which may occur anywhere or almost anywhere in the dis¬ tribution there are two more distinct local forms, each of which is regarded by Coutagne as probably constituting a fresh mode, perhaps compatible with the others.