Page:Popular Science Monthly Volume 48.djvu/617

Rh from the possession of the same variation by the animal with which it is mated; and this belief is held by men who, as breeders, stake large profits on its truth. How, then, can it be said that without the union of two similarly varied individuals, "the new breed would never even begin, let alone the question of its perpetuation after it had begun." And here, to show still more clearly how experience negatives Lord Salisbury's assumption, let me give some evidence furnished not by domestic animals, but by human beings. Referring to a controversy which I have recently been carrying on with Prof. Weismann, Dr. Lindsay Johnson, F.R.C.S., who practices as an ophthalmic surgeon, and who tells me that the experience of other oculists verifies his own, testifies to the transmission of acquired myopia through several generations. He says (I quote with his permission):—

And he sends me a genealogical tree showing that in a family of six children descending from long-sighted ancestry on both sides, four remained normal-sighted, but two, who were miniature painters, became myopic. Of these one, marrying a normal-sighted wife, had two children, of whom one was myopic; and the other, marrying also a normal-sighted wife, had three children, all myopic. Two of these three married normal-sighted wives, and among their children there was in each case one who had become myopic, while the rest are as yet too young to display the defect, for it never occurs until after eight years old. That the inherited trait is in this case one caused by use, and not one arising spontaneously, does not affect the issue. There is proof that a modification of structure existing in one parent may descend to children when no similar modification is possessed by the other parent; and, further, that this modification may be re-transmitted, also without the aid of the second parent: facts which negative Lord Salisbury's assumption.

Let us now consider what is the corollary as respects modification of varieties and formation of species. Travelers tell us that the Bushmen are so long-sighted that they can see as far with the naked eye as a European can with a telescope. Allowing for some exaggeration, it is safely to be inferred that they have marvelous powers of discerning objects at great distances. How has this trait arisen? Small men as they are, wandering about in single families, Bushmen have to guard against enemies, brute and