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.

    172/290 (page 150)
    150 PROBLEMS OF GENETICS Guillemot ( Uria traile) which has a white line round the eyes and at the sides of the head where the normal has no such mark; but this line is formed in a very special place, the groove joining the eye to the ear, whereas the feathers of the nuchal crescent are not ostensibly distinguished from those adjacent.® The transposition of the brown and the grey on the back and front of the neck also constitutes a very remarkable difference. If either grey or brown depends on a factor then it must be sup¬ posed that auratus has one of these factors and cajer the other. From these several considerations it is quite clear that if auratus and cajer are modifications of the same type produced by presence or absence of factors, several independent elements must be concerned, and to unravel their inter-relations would be most difficult even if it were possible to breed the types under ob¬ servation, which is of course quite beyond present possibilities. The distribution of the two is as follows. On the east side of the Continent C. auratus, relatively pure, occupies the whole of Canada and the States from the North to Galveston. Westward it extends across the whole continent in the more northern region to Alaska, but in its pure form it only reaches down the Pacific coast to about the northern border of British Columbia. Its southern and western limit is thus roughly a line drawn from north of Vancouver, southeast to North Dakota and then south to Galveston. C. cafer in the comparatively pure form inhabits Mexico, Arizona, California (except Lower California and the opposite coast), central and western Nevada, Utah, Oregon, and is bounded on the east by a line drawn from the Pacific south of Washington, south and eastward through Colorado to the mouth ® This variety is spoken of as the Ringed Guillemot and is sometimes regarded as a distinct species to which the name ringvia was given by Brünnich. In sup¬ port of this view Dr. William Brewster, to whom I am indebted for much assist¬ ance in regard to the variation of birds, called my attention to observations of his own and also of Maynard's, that the ringed birds were sometimes mated together, though in a small minority (see Brewster, Proc. Boston Soc. N. H., XXII, 1883, p. 410). It would however be possible to produce many instances of varieties mated together though surrounded by a typical population (e. g., two varying Black¬ birds, ZooZogi si, p. 2765; two varying Nightjars, ibid., p. 5278). I am inclined to believe that in nature matings between brothers and sisters are frequent in many species of animals, and that the production of sporadically varying colonies is thus greatly assisted.