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Show XII. DURATION AND ORIGINATION OF RACE .AND SPECIEB.IMPORT OF SEXUAL REPRODUCTION. I. .Do Varieties wear out, or tend to wear out f (NEW Y Ol~K TRlliUNE, and AMERinAN J OURN.AL OF SCIENCE .AND TllE All.Til, February, 1875.) Tnrs question has been argued from time to time for more than ha.lf a century, and is far from being settled yet. Indeed, it is not to be settled either way so easily as is sometimes thought.. The result of a prolonged and rather lively discussion of the topic about forty y"ears ago in England, in which Lindley bore a leading part on the negative side, was, if we rightly remember, that the nays bad the best of the argument. The deniers could fairly well explain away the facts adduced by the other side, and evade the force of the reasons then assigned to prove that varieties were bound to die out in the course of time. But if the case were fully re-argued now, it is by no means certain that the nays would win it. The most they could expect would be the Scotch verdict, " not proven.~' And this not because much, if any, add~tional evidence of the actual wearing out of any van- DURATION OP RAOES. 339 ety has turned up since, but because a presumption has been raised under which the evidence would take a pias the other way. There is now in the minds of scientific men some reason to expect that certain vari- . eties would die out in the long nm and this miO'ht ' 0 have an important influence upon the interpretation of the facts. Curiously enouO'h, however the recent discussions to which our att~~tion has been called seem, on both sides, to have overlooked this. But, first of alJ, the question needs to be more specifically stated. There are varieties and varieties. They may, some of them, disappear or deteriorate, but yet not wear out-not come to an ~d from any inherent cause. One might even say, the younger they are the less the chance of survival unless well cared for. They may be smothered out by the adverse force of superior numbers; they are even more likely to be bred out of existence by unprevented cross-fertilization, or to disappear from mere change of fashion. The question, however, is not so much about reversion to an ancestral state, or the falling off of a high-bred stock into an inferior condition. Of such cases it is enough to say that, when a variety or strain, of animal or vegetable, is led up to unusual fecundity or of size or product of any organ, for our good, and not for the good of the plant or animal itself, it can be kept so only by high feeding and exceptional care; and that with high feeding and artificial appliances comes vastly increased liability to disease, _which may practically annihilate the race. But then the race, like the bursted boiler, could not be said to wear out, while if left to ordinary conditions, and allowed to degenerate back into a more |