Birth-variation is then an inherent property of living things (including man) as much as heredity, which is the name for the property expressed in the resemblance of offspring to parent. And birth-variation, or congenital variation--that is to say, the being born with a power to grow into something different (not greatly, but still obviously, different) from their parents or ancestry, and from their brethren and cousins, though not subjected after birth to any treatment or conditions differing from those common to all of them--is a quality of living things which must be distinguished altogether from the power of the individual itself, though not born with qualities differing from those of its brothers and sisters, to vary or change in some respects as compared with other individuals when it is specially fed or exposed to special treatment. The first is change, or variation, of the “stirps,” or germ plasm; the second is change, or variation, of the transient body of the individual. The first is indefinite and may be of almost any kind or form; once it has appeared, it is a permanent possession of the race descended from its owner. The second is definite and a direct reaction to the environment. Such an individually induced or stimulated change is often called an “acquired character.” It does not affect the stirps, the inner reproductive germs, and cannot be handed on by inheritance to a new generation. What happens, then, when there is a cessation of selection? All sorts of birth-variations appear and grow up. The fine adjustment of form--maintained by natural selection carried on unceasingly--no longer obtains. The characteristics of the race become less emphasised. All sorts of birth-variations have an equal chance, and the tendency must be for those characteristics which have most recently been established and maintained by severe selection to dwindle and then to disappear altogether. The majority of birth-variations will--when selection is prevented--always tend to present a lessened, rather than an increased, development of any one characteristic--the excelling minority will no longer be selected, but all will have an equal chance in mating and reproducing. Hence, bit by bit, all salient features, all the characteristics of the race previously maintained by selection, will, as a result of survival of all variations and general crossing and interbreeding--dwindle and disappear. It is to this process that the term “degeneration” has been applied by biologists. How far it may go, and what are its limits and various outcomes, I cannot now discuss. It is sometimes spoken of as “retrogression”--which implies wrongly a return to a previous state. From some points of view it might be called “simplification.”