72 Variation 
knows that Darwin was always very careful in statements of this 
kind. 
From the same chapter I may here cite the following paragraph: 
“Thus as I am inclined to believe, morphological differences,... 
such as the arrangement of the leaves, the divisions of the flower or 
of the ovarium, the position of the ovules, etc.—first appeared in 
many cases as fluctuating variations, which sooner or later became 
constant through the nature of the organism and of the surrounding 
conditions...but not through natural selection’; for as these morpho- 
logical characters do not affect the welfare of the species, any slight 
deviation in them could not have been governed or accumulated 
through this latter agency®.” We thus see that in Darwin’s opinion, 
all small variations had not the same importance. In favourable 
circumstances some could become constant, but others could not. 
Since the appearance of the first edition of The Origin of Species 
fluctuating variability has been thoroughly studied by Quetelet. He 
discovered the law, which governs all phenomena of organic life 
falling under this head. It is a very simple law, and states that 
individual variations follow the laws of probability. He proved it, 
in the first place, for the size of the human body, using the measure- 
ments published for Belgian recruits; he then extended it to various 
other measurements of parts of the body, and finally concluded 
that it must be of universal validity for all organic beings. It must 
hold true for all characters in man, physical as well as intellectual 
and moral qualities; it must hold true for the plant kingdom as 
well as for the animal kingdom; in short, it must include the whole 
living world. 
Quetelet’s law may be most easily studied in those cases where 
the variability relates to measure, number and weight, and a vast 
number of facts have since confirmed its exactness and its validity 
for all kinds of organisms, organs and qualities. But if we examine 
it more closely, we find that it includes just those minute variations, 
which, as Darwin repeatedly pointed out, have often no significance 
for the origin of species. In the phenomena, described by Quetelet’s 
law nothing “happens to arise”; all is governed by the common 
law, which states that small deviations from the mean type are 
frequent, but that larger aberrations are rare, the rarer as they are 
larger. Any degree of variation will be found to occur, if only the 
number of individuals studied is large enough: it is even possible 
to calculate beforehand, how many specimens must be compared in 
order to find a previously fixed degree of deviation. 
The variations, which from time to time happen to appear, are 
evidently not governed by this law. They cannot, as yet, be pro- 
} The italics are mine (H. de V.). 2 Origin of Species (6th edit.), p. 176. 
