Page:Popular Science Monthly Volume 48.djvu/690

618 with the slow growth of a complicated civilization and an increased demand for horses.

As inheritance has an influence on the price of horses, what will be the result if we destroy the children of all horses which fetch less than +2 of Galton's scheme, and breed only from that fourth of the whole which sell for more than 75° of his centesimal scale?

We may at first get fancy prices for our expensive stock, but if selection cease with this first step, and we supply as many colts as before, while the demand remains unchanged, the price will "revert" to the type, and the mean will become the same as it was.

Does this prove that those qualities in horses for which money is paid have "retrograded to mediocrity" in these descendants of high-priced parents? It proves nothing of the sort, for the qualities which command a price are one thing and the price another. Even if the horses have much more of these qualities than the old stock, the price will still be fixed by the ratio between demand and supply, and while blood will tell in use it will not tell in price.

It is clear, then, that characteristics of living things which are influenced by inheritance may conform to a type which exhibits "specific stability," "regression to mediocrity," an occasional "sport," and all the other properties of the types which Galton has studied, without furnishing proof that "inherited" qualities behave in the same way. To prove this we must cancel, or neutralize, or make allowance for all the factors which have an influence upon the type, except "inheritance."

Galton's generalizations upon the laws of inheritance from the statistical study of finger prints rests upon the belief that the patterns are inherited. If they are not, they can teach nothing of inheritance. He proves by statistics that they are, to some degree, dependent either directly or indirectly upon inheritance, just as the price of horses is, but this is not enough. To warrant his deductions he must prove that inheritance is the controlling factor in determining the type; that, in the long run, all the other factors will balance; and this, it seems to me, he fails to prove. He has studied in one hundred and fifty fraternal couples or children of the same parents the frequency with which the same pattern occurs on the same digit of both, and he finds that when marked on a scale in which indicates no resemblance and 100° the greatest possible relationship, they show 10° of relationship. This number is great enough to prove the influence of inheritance, but it is too small to show that the patterns are themselves directly inherited, and it seems to indicate that they are indirectly influenced by some other inherited characteristic, such perhaps as the ratio between the growth in the embryo of the ball of the finger and that of the nail.