538 THE AMERICAN JOURNAL OF SOCIOLOGY
Under exceptional circumstances, as when exposed to novel and powerful influences, the whole race is sometimes rendered really degenerate, as is proved by the deterioration of European dogs in India and horses in the Falkland Islands. But the mere fact of deterioration under novel conditions proves clearly how necessary for the preservation of the race is a high degree of insusceptibility to the influences to which the race is normally exposed. In view of the indisputable fact that races undergo evolution, not degenera- tion, when exposed to disease and alcohol, the medical doctrine of heredity amounts in effect to this, that if only a race goes down hill long enough, it will ultimately arrive at the top. It is literally inconceivable that evolution can have resulted from continuous degeneration.
We must conclude, therefore, that variations are very rarely due to the direct action of the environment on the germ-plasm. This conclusion is confirmed by another set of facts, which serve also to indicate the true source of variations the true reason why offspring differ innately from their parents. The members of a litter of dogs, cats, or pigs always vary, not only from their parents, but among themselves, and may vary very greatly. Thus one puppy may be large, strong, vigorous, dark, and rough-haired ; while others may exhibit different qualities in all sorts of com- binations. One puppy may resemble the father, another the mother, and a third some distant ancestor. Obviously, their extreme variations cannot be due to the action of environment; for all the germ-cells and all the puppies before birth were placed under conditions that were practically identical. We have no choice, therefore, but to believe that the variations of the litter are spontaneous; in other words, that their source lies in the nature of the germ-plasm, not in the action of the environment. We know that a germ-cell, on being fertilized, spontaneously produces many different kinds of body-cells, such as skin- and muscle-cells. In just the same way it produces spontaneously germ-cells which differ among themselves. These variations are absolutely neces- sary to the persistence of the species. Otherwise natural selection would have no material to work on. Children would be exact copies of the parent, and the race could not adapt itself to changes
