Note 5 — Chapter VII

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 support of this view Dr. William Brewster, to whom I am indebted for much assistance 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 Blackbirds, Zoologist, 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.