10), showing the variation among forty males
of Agelaeeus phoeniceus, this approach to an equable spreading of the
variations is still more apparent; while in Fig. 12, where fifty-eight
specimens of Cardinalis virginianus are registered, we see a remarkable
spreading out of the spots, showing in some of the characters a tendency
to segregation into two or more groups of individuals, each varying
considerably from the mean.
[Illustration: FIG. 9]
[Illustration: FIG. 10.]
[Illustration: FIG. 11.]
In order fully to appreciate the teaching of these diagrams, we must
remember, that, whatever kind and amount of variations are exhibited by
the few specimens here compared, would be greatly extended and brought
into symmetrical form if large numbers--thousands or millions--were
subjected to the same process of measurement and registration. We know,
from the general law which governs variations from a mean value, that
with increasing numbers the range of variation of each part would
increase also, at first rather rapidly and then more slowly; while gaps
and irregularities would be gradually filled up, and at length the
distribution of the dots would indicate a tolerably regular curve of
double curvature like those shown in Fig.
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