Darwin and After Darwin (Volume 3); Post-Darwinian Questions Isolation and Physiological Selection. 1897

Paperback / softback
This historic book may have numerous typos, missing text or index. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. 1897. Not illustrated. Excerpt: ... chapter vi. A Brief History Of Opinions On Isolation As A Factor Of Organic Evolution. This historical sketch must begin with a consideration of Darwin's opinions on the subject; but as these were considerably modified from time to time during a period of thirty years by the publications of other naturalists, it will be impossible to avoid crossreferences as between his writings and theirs. It may also be observed that the Life and Letters of Charles Darwin was not published until the year 1887, so that the various opinions which I shall quote from the letters, and which show some considerable approximation in his later years to the views which have been put forward by Mr. Gulick and myself, were not before us at the time when our papers were read. The earliest allusion that I can find to geographical isolation in the writings of Darwin occurs in a correspondence with Sir Joseph Hooker, as far back as 1844. He there says: --I cannot give my reasons in detail; but the most general conclusion which the geographical distribution of all organic beings appears to me to indicate is, that isolation is the chief concomitant or cause of the appearance of new forms (I well know there are some staring exceptions)'. And again: --With respect to original creation or production of new forms, I have said that isolation appears the chief element. Next, in the earlier editions of the Origin of Species this view is abandoned, and in its stead we meet with the opinion that geographical isolation lends a certain amount of assistance to natural selection, by preventing free intercrossing. But here we must note two things. First, the distinction between monotypic and polytypic evolution is not defined. Secondly, the levelling effecjLjofJjee intercrossing in nature, and hence its antago...