An Introduction to a Biology; And Other Papers

Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: II On the Bearing of Mendelian Principles of Heredity on Current Theories of the Origin of Species textit{(Manchester Memoirs, Vol. xlviii., 1904, textit{No. 24) A Wide field of work and speculation has been opened up to the student of evolution by Mendel; and by his followers it has been maintained that it is only by working on the lines laid down by the Abbot of Briinn that a solution of the problem of the origin of species can ultimately be reached. It is the object of this paper to show the rela tion which Mendel's work bears to current theories of organic evolution. (1) On The Difference Between Continuous And DisContinuous Variation For an account of continuous variation the reader is referred to the Presidential Address to Section D of the British Association, at the Bristol Meeting, by Professor Weldon (Weldon, '98): discontinuous variation is set forth by Mr. Bateson in his work Materials for the Study of Variation (Bateson, '99); all that remains for me to do ie to call attention to some of the differences between these two conceptions of variation. Continuous variation is the name of a phenomenon of everyday observation, namely, the fact that no two individuals of a species (plant or animal) are alike; it is a permanent quality of all animal? and plants at all times, tending, as far as we can see, in any direction (and as little, textit{Vide List of Authorities, p. 139 textit{infra. teleological in any sense of the word as anything can be imagined to be). Above all, cases of continuous variation can be described by curves of error, a fact which seems to me to have a very deep meaning. Discontinuous variation is the quality which animals and plants possess of giving rise, from time to time, to offspring bearing characters specifically ...