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As the variability of each species is an independent property, and will be taken advantage of by natural selection, only so far as it profits the individual in its complex struggle for life, so the degree of modification in different species will be no uniform quantity.
Hence it is manifest that even the results of such a highly improved technical method do not deserve the confidence usually put in them. They are open to doubt, and the highest figures do not really indicate the best representatives of the race. In order to convey this conception to you in a still stronger manner, let us consider the partial variability as it usually shows itself.
In the long run selection gains the day, and we do not expect to fail so far as to breed a bird as coarse as a common tumbler from a good short-faced strain. But as long as selection is rapidly going on, there may always be expected to be much variability in the structure undergoing modification.
He had tried to stand off and reach a point of view, to become a spectator, while the only way to fit into the century was simply to keep moving in whirls of unintelligent unison; never to meditate, never to reason upon one's course; but to sweep onward, somewhere, anywhere as long as it was in a new direction. Elasticity, variability were not these the indispensable qualities of the modern mind?
Leaving aside polymorphy, we may now discuss those cases of variability, in which the changes themselves, and not only their final results play a part. Of such changes two types exist.
On the other hand we have evidence that variability, when it has once come into play, does not cease under domestication for a very long period; nor do we know that it ever ceases, for new varieties are still occasionally produced by our oldest domesticated productions.
To escape it, different names would have to be given to the two kinds of order, and that is not easy, because of the variety and variability of the forms they take. The order of the second kind may be defined as geometry, which is its extreme limit; more generally, it is that kind of order that is concerned whenever a relation of necessary determination is found between causes and effects.
If this is done, and the ordinates are arranged at equal distances, the line which unites their summits is the desired curve. At first glance it exhibits a form quite analogous to the curves of fluctuating variability, obtained by the measurements of beans and in other instances.
We shall have to recur to this subject; and I will here only add that their variability seems to result from their uselessness, and consequently from natural selection having had no power to check deviations in their structure. Several years ago I was much struck by a remark to the above effect made by Mr. Waterhouse. Professor Owen, also, seems to have come to a nearly similar conclusion.
The cause lies in the enormous difficulties attached to grafting or budding of these trees, which make this method very expensive and to a high degree uncertain and unsatisfactory. After this hasty survey of the more reliable facts of the practice of an asexual multiplication of the extremes of fluctuating variability, we may now return to the previously mentioned theoretical considerations.
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