Weismann, A. (1904). Lecture XXVI. Germinal selection (continued) (J. A. Thomson & M. R. Thomson, Trans.). In A. Weismann & J. A. Thomson, M. R. Thomson (Trans.), The evolution theory, Vol. 2, pp. 136-158). London, Great Britain: Edward Arnold.
http://dx.doi.org/10.1037/13696-007
Hitherto we have derived the variations of the determinants of the germ-plasm, upon which we based the process of germinal selection, from chance local fluctuations in nutrition, such as must occur in an individual id, independently of the nutrition of the other ids of the same germ-plasm. But there are doubtless also influences which set up similar nutritive changes in all ids, and by which, therefore, all homologous determinants, in as far as they are sensitive to the nutritive change in question, are affected in the same manner. To this category belong changes in the external conditions of life, and particularly climatic changes. It is, then, germinal selection alone which brings about the presence of a majority of ids with determinants varying in the same direction, and personal selection has no part in the transformation of the species. (PsycINFO Database Record (c) 2016 APA, all rights reserved)