Page:Popular Science Monthly Volume 78.djvu/547

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MEASUREMENT OF NATURAL SELECTION

twenty-one cases to seven the asymmetry of matured fruits is less than that of the ovaries which do not complete their development. Taken as a whole, the differences show an unmistakable tendency to fall far to the negative side of the 0 bar.

Not merely the degree of radial asymmetry of the ovary, but the number of its locules which have an odd number of ovules, seems to be of consequence in determining whether an ovary shall complete its development. Ovaries with even numbers—6, 8, 10, 12—of ovules in their locules have a better chance of developing to maturity than do those with one or more locules with an odd number. The question is too involved for adequate discussion, and I will leave the subject with a mere reference to Fig. 7 which shows that in the 1908 series the reduction in the percentage of "odd" locules is a very material one.

PSM V78 D547 Percentage of odd locules in eliminated and matured ovaries of staphylea 1908.png
Fig. 7. Percentage of "Odd" Locules in eliminated and matured Ovaries of Staphylea—1908 collection.

The work just outlined has been rather drastically criticized on the ground that studies on the selective elimination of organs can never have any bearing on the problem of evolution. I think there is room for differences of opinion on this point, but at present the purely morphogenetic and physiological sides of the problem are of paramount interest; our knowledge of facts is too meager to justify speculations on so complex a problem as that of the origin of species.

IV. Concluding Remarks

In the paragraphs which have preceded these I have tried to set forth honestly the results which have been secured in attempts to ascertain by direct quantitative methods the intensity of the selective elimination which may occur in nature.

What is the general significance of these results? What claim have they to the special attention of scientific men?

First, let us premise that the measurement of natural selection is not synonymous with such an expression as the demonstration of the natural selection theory. Upon the application of biometric methods many supposedly valid biological theories have shrunken to nothing;