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Quetelet's experiments with the dynamometer on university students showed the same results: first ranked the Englishman, then the Frenchman, then the Belgian, then the Russian, then the Southern European: for those races of Southern Europe which once ruled the Eastern and the Western worlds by physical and mental power have lost in strength as they have paused in civilization, and the easy victories of our armies in Mexico show us the result.
Fortunately, Quetelet's law is a very clear and simple one, and quite sufficient for our considerations. It claims that for biologic phenomena the deviations from the average comply with the same laws as the deviations from the average in any other case, if ruled by chance only. The meaning of this assertion will become clear by a further discussion of the facts.
This study has for its main object the production of sugar in the stems, and the curves, which indicate the percentage of this important substance in different stems of the same variety, comply with Quetelet's law.
Quetelet's law of variation had not yet been published. Mendel's claim of hereditary units for the explanation of certain laws of hybrids discovered by him, was not yet made. The clear distinction between spontaneous and sudden changes, as compared with the ever-present fluctuating variations, is only of late coming into recognition by agriculturists.
This very important point however, will be reserved for the next lecture, and only the facts available at present will be considered here. As a first example we may take the ray-florets of the composites. On a former occasion we have dealt with their fluctuation in number and found that it is highly variable and complies in the main with Quetelet's law.
For here the dark brown spots vary between nearly complete deficiency up to such predominancy as almost to hide the pale yellow ground-color. After this hasty survey of the causes of fluctuating variability, we now come to a discussion of Quetelet's law. It asserts that the deviations from the average obey the law of probability. They behave as if they were dependent on chance only.
But even the hybrids of the best parents may be improved, because they are no less subject to Quetelet's law than any other strain. Any large number of hybrids of the same ancestry will prove this, and often the excellency of a hybrid variety depends chiefly, or at least definitely, on the selection of the best individuals.
Darwin's hypothesis of natural selection as the means by which new types arise, is now being generally interpreted as stating the slow transformation of ordinary fluctuating divergencies from the average type into specific differences. But in doing so it is overlooked that Quetelet's law of fluctuating variability was not yet discovered at the time, when Darwin propounded his theory.
The variation of the number of the rows is easily seen to comply with Quetelet's law, and often 30 or 40 ears suffice to give a trustworthy curve. Fritz Muller made some experiments upon the inheritance of the number of the rows, in Brazil. He chose a race which averaged 12 rows, selected ears with 14, 16 and 18 rows, etc., and sowed their kernels separately.
The lack of more definite knowledge upon this matter was keenly felt by Darwin, and exercised much influence upon his views at various times. Quetelet's famous discovery of the law of fluctuating variability changed the entire situation and cleared up many difficulties.
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