Similarly with variation, the demands of his hypothesis are very slight. If it be conceded that variation is a fact, that offspring do vary from their parents and each other, it is enough. And who will dispute this in a world where no two creatures are exactly and in all particulars alike? The apparent contradiction that, heredity demands likeness, while variation requires difference, is confined to the surface--it is not real. The likeness is general while the difference is particular. A sheep may be born with shorter or longer legs, by variation; but it will be a sheep and not a horse, by heredity. As an example of the working of the theory let us take Lamarck’s piece de resistance, the giraffe. Lamarck says: “We know that this animal, the tallest of mammals, inhabits the interior of Africa, and that it lives in localities where the earth, almost always arid and destitute of herbage, obliges it to browse on the foliage of trees and to make continual efforts to reach it. It has resulted from this habit, maintained for a long period in all the individuals of its race, that its forelegs have become longer than the hinder ones, and that its neck is so elongated that the giraffe, without standing on its hind legs, raises its head and reaches six meters in height (almost twenty feet).” Lamarck thought this length of neck was acquired by “continual efforts to reach,” or, as Alfred Russell Wallace puts it in his criticism of Lamarck--“stretching.” Many critics ventilated their wit on this theory of Lamarck’s, under the impression that they were lampooning Darwin’s idea. They made a blunder similar to that of those critics of Utopian Socialism who labor under the pleasing delusion that they are riddling the theories of Marx. Professor Ritchie has preserved a couple of stanzas by a witty Scotch judge who aimed his poem at Darwin, but hit Lamarck. “A deer with a neck that was longer by half Than the rest of his family, try not to laugh, By stretching and stretching became a giraffe Which nobody can deny. That four-footed beast which we now call a whale, Held his hind-legs so close that they grew to a tail, Which he uses for threshing the sea, like a flail, Which nobody can deny.” But Darwin’s theory is altogether independent of the “stretching” idea. The causes and origin of heredity and variation are up to this moment, alike wrapped in mystery. But when science succeeds in penetrating those secrets, it is extremely unlikely that Darwin’s theory will be seriously weakened, no matter what the causes may prove to be.