As a result of his observations on the Beagle, Darwin became possessed with the idea, which of course had occurred to various thinkers before him, from the Greeks to Lamarck, that life had not been created in distinct manifold forms, but had developed in all its variety, including even man, from a few forms, or even from one. To entertain the idea in the abstract was comparatively simple; but to explain the process of development was the puzzle, until Darwin hit upon what seemed to him the clue in what he called ‘natural selection,’ or, as Spencer termed it, ‘the survival of the fittest.’ For twenty years Darwin patiently worked out experimental proof of this theory, and then in 1859 he published ‘The Origin of Species,’ a book which is generally admitted to be one of the most important in the whole history of science. During the remaining twenty years of his life he devoted himself to endless further experiment, and the results were embodied in numerous volumes, chief among which was ‘The Descent of Man.’ His views were from the first the subject of fierce controversy, and in many details they are still so, and will continue to be. But it may safely be said that in the scientific world the evolution of life, or more technically, modification by descent, which is so inseparably associated with Darwin’s name, is an accepted principle, and Darwin himself had the great and satisfying triumph of living until this acceptance was perceived to be general, if not universal. He was buried in Westminster Abbey, close to the last resting-place of Newton. The basis, or at any rate one of the most fundamental elements of Darwin’s character, was the instinct and habit of observing the external world, and we can best approach him by considering this habit in others and in him. It is astonishing how little most of us see. We live in a world of shadows and dream outlines, piecing out reality by convenient abstractions, which pass in memory like worn current counters, with little resemblance to actual fact. A tree to us is vaguely a tree: the structure of its bark, the shape of its leaves do not enter our world. A man and a woman are simply—a man and a woman. Unless we are specially called upon to do so we do not note details of feature or gesture or garment. This vagueness, this abstraction of vision, is what Théophile Gautier referred to in his celebrated phrase, ‘I am a man for whom the visible world exists.’[1] And he amplified his idea by saying that of twenty-five persons who come into a room, twenty-four will go out and not be able to tell you the color of the wall-paper, whereas he could tell that and pretty much everything else. To such an observing temperament life is a matter of visual detail, of sensuous detail of every kind.