Page:The Evolution of British Cattle.djvu/105

 and partly as seeds—from the potato-field at Hilversum to the botanic garden at Amsterdam.

"The three stocks gave rise under cultivation to many thousands of individuals, which bred true along certain lines, and yet gave rise to other new forms. In short, De Vries had found a plant in the process of evolution.

"The predisposition to mutability—which remains a mystery—was present. De Vries gave it scope, and like the primeval gardener he had the pleasure of giving names to a crop of new creations which emerged before him. From each of these three samples there arose distinctive groups—which, if they had been found in nature, would have been reckoned as distinct species of evening primrose. But the most interesting feature was the apparent abruptness in the origin of the new forms. They seemed to rise by leaps and bounds, by organic jerks; they illustrated what De Vries has called 'mutation.'"

It does not concern us here whether De Vries 's mutations were the result of a new environment or of some other cause. The point for us is that while there may be variation in the Darwinian sense, there are also sudden changes when animals of different characters are bred together, and under certain circumstances these changes are inherited. Mendel's theory explains both the changes and their inheritance. Mendel's original experiments were made with