In the first year of the present century, Lamarck followed Erasmus Darwin’s lead with an open avowal that in his belief all animals and plants were really descended from one or a few common ancestors.  He held that organisms were just as much the result of law, not of miraculous interposition, as suns and worlds and all the natural phenomena around us generally.  He saw that what naturalists call a species differs from what naturalists call a variety, merely in the way of being a little more distinctly marked, a little less like its nearest congeners elsewhere.  He recognised the perfect gradation of forms by which in many cases one species after another merges into the next on either side of it.  He observed the analogy between the modifications induced by man and the modifications induced by nature.  In fact, he was a thorough-going and convinced evolutionist, holding every salient opinion which Society still believes to have been due to the works of Charles Darwin.  In one point only, a minor point to outsiders, though a point of cardinal importance to the inner brotherhood of evolutionism, he did not anticipate his more famous successor.  He thought organic evolution was wholly due to the direct action of surrounding circumstances, to the intercrossing of existing forms, and above all to the actual efforts of animals themselves.  In other words, he had not discovered natural selection, the cardinal idea of Charles Darwin’s epoch-making book.  For him, the giraffe had acquired its long neck by constant reaching up to the boughs of trees; the monkey had acquired its opposable thumb by constant grasping at the neighbouring branches; and the serpent had acquired its sinuous shape by constant wriggling through the grass of the meadows.  Charles Darwin improved upon all that by his suggestive hint of survival of the fittest, and in so far, but in so far alone, he became the real father of modern biological evolutionism.

From the days of Lamarck, to the day when Charles Darwin himself published his wonderful ‘Origin of Species,’ this idea that plants and animals might really have grown, instead of having been made all of a piece, kept brewing everywhere in the minds and brains of scientific thinkers.  The notions which to the outside public were startlingly new when Darwin’s book took the world by storm, were old indeed to the thinkers and workers who had long been familiar with the principle of descent with modification and the speculations of the Lichfield doctor or the Paris philosopher.  Long before Darwin wrote his great work, Herbert Spencer had put forth in plain language every idea which the drawing-room biologists attributed to Darwin.  The supporters of the development hypothesis, he said seven years earlier—­yes, he called it the ‘development hypothesis’ in so many words—­’can show that modification has effected and is effecting great changes in all organisms, subject to modifying influences.’  They can show, he goes on (if I may venture to condense