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Show 100 THE rERPETUA'riON Ol!' LIVING BEINGS, were introduced; ancl ns their wool was much n1ore valuable, and as they were a quiet race of sheep, and showed no tenclency to trespass or jump over fences, the Otter breed of sheep, the wool of which was inferior to that of the Merino, was gradually allowed to die out. You sec that these facts illustrate perfectly well what may be done if you take care to breed from stocks that are similar to each other. After having got a variation, if, by crossing a variation with the original stock, you multiply that variation, and then take care to keep that variation distinct from the original stock, ancl make them breed together,-then you may almost certainly produce a race whose tendency to continue the variation is exceedingly strong. This is what is called "selection;" and it is by exactly the same process as that by which Seth vVright bred his Ancon sheep, that our breeds of cattle, dogs, and fowls, are obtained. There are some possibilities of exception, but still, speaking broadly, I may say that this is the way in which all our varied races of domestic animals have arisen; and you must understand that it is not one peculiarity or one characteristic alone in which animals may vary. rrhere is not a single peculiarity or characteristic of any ki~d, bodily or mental, in which offspring may not vary to a certain extent from the parent and other animals. Among ourselves this is \vell known. The simplest physical peculiarity is mostly reproduced. I know a case of a man whose wife has the lobe of one of her ears a little flattened. An ordinary observer might IIEREDITAll.Y TRANSMISSION AND VARIATION. 101 scarcely notice it, and yet every one of her children has an approximation to the same peculiarity to some extent. If you look at the other extreme, too, the gravest diseases, such as gout, scrofula, and consumption, may be handed down with just the same certainty ancl persistence as we noticed in the perpetuation of the bandy legs of tbe A.ncon sheep. However, these facts are best illustrated in animals ) and the extent of the variation, as is well known, is very remarkable in dogs. For example, there are some dogs very much smaller than others; indeed, the variation is so enormous that probably the smallest dog would be about the size of the head of the larcrest · b ' there are very great variations in the structural forms not only of the skeleton but also in the shape of the skull, and in the proportions of the face and the disposition of the teeth. rrhe Pointer, the Retriever, Bulldog, and the Terrier, differ very . greatly, and yet there is every reason to believe that every one of these races has arisen from the same source,-that all the most important races have arisen by this selective breeding from accidental variation. A ~till more. striking case of what may be done by selectlYe breeding, and it is a better case, because there is no chance of that partial infusion of error to which I. alluded, has been studied very carefully by Mr. Darw1n,-the case of the domestic pigeons. I dare say there may be some among you who mav be pigeon fanciers, and I wish you to understand ~hat in approaching the subject, I would speak with all |