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Show 30 JJARWINIANA. The common proposition is, that species reproduce tlwir li~e; this is a sort o:f general inference, only a . degree closer to :fact than the statement that genera reproduce their like. The true. proposition, the :fact incapable o:f :further analysis, .is, that ilndividuals reproduce tl~eir like-that characteristics are inheritable. So varieties, or deviations, once originated, are perpetuable, like species. Not so likely to be perpetuated, at the outset; for the new :form tends to resemble a grandparent and a long line o:f similar ancestors, as well as to resemble its immediate progenitors. Two :forces which coincide in the ordinary case, where the o:ff8·pring resembles its parent, act in different directions when it does not and it is uncertain which will prevail. If the remoter but very potent ancestral influence predominates, the variation disappears with the life o:f the individual. If that o:f the immediate parent-:feebler no doubt, but closer-the variety survives in the offspring; whose progeny now has a redoubled tendency to produce its own like ; whose progeny again is almost sure to produce ·its like, since it is much the same whether it takes a:fter its mother or its grandmother. In this way races arise, which under :favorable conditions may be as hereditary as species. In following these indications, watching opportunities, and breeding only :from those individuals which vary most in a desirable direction, man leads the course o:f variation a~ he leads a streamlet-apparently at will, but never against the :force o:f gravitation-to a long distance :from its source, and makes it more subservient to his use or :fancy. He unconsciously strengthens those THE ORIGIN OF SPECIES. 31 variations which he prizes when be plants the seed o:f a favorite :fruit, preserves a favorite domestic animal, drowns the uglier kittens of a litter, and allows only the handsomest or the best mousers to propagate. Still more, by methodical selection, in recent times almost marvelous results have been produced in new breeds o:f cattle, sheep, and poultry, and new varieties of :fruit of greater and greater size or excellence. · It is said that all domestic varieties, if le:ft to run wild, would revert to their aboriginal stocks. Probably they would wherever various races of one species were le:ft to commingle. At least the abnormal or exaggerated characteristics induced by high :feedinO', or high cultivation and prolonged close breeding, w~uld promptly disappear; and the surviving stock would soon blend into a homogeneous result (in a way presently explained), which wouJd naturally be taken for the original :form; but we could seldom know if it were so. It is by no means certain that the result would be the same if the races ran wild each in a separate region. Dr. Hooker doubts if there is a true reversion in the case of plants. Mr. Darwin's observations rather :favor it in the animal kingdom. With mingled races reversion seems well made out in the case of pigeons. The common opinion upon this subject therefore probably has some foundation. But even i:f we regard varieties as oscillations around a primitive centre or type, still it appears from the readiness with which such varieties originate that a certain amount o:f disturbance would carry them beyond the influence o:f the primordial attraction, where they may become new centres o:f variation. |