ach species as a special act of creation, there is no apparent
reason why more varieties should occur in a group having many species,
than in one having few.

To test the truth of this anticipation I have arranged the plants of
twelve countries, and the coleopterous insects of two districts, into
two nearly equal masses, the species of the larger genera on one side,
and those of the smaller genera on the other side, and it has invariably
proved to be the case that a larger proportion of the species on the
side of the larger genera present varieties, than on the side of the
smaller genera. Moreover, the species of the large genera which present
any varieties, invariably present a larger average number of varieties
than do the species of the small genera. Both these results follow when
another division is made, and when all the smallest genera, with from
only one to four species, are absolutely excluded from the tables.
These facts are of plain signification on the view that species are only
strongly marked and permanent varieties; for wherever many species of
the same genus have been formed, or where, if we may use the expression,
the manufactory of species has been active, we ought generally to find
the manufactory still in action, more especially as we have every reason
to believe the process of manufacturing new species to be a slow one.
And this certainly is the case, if varieties be looked at as incipient
species; for my tables clearly show as a general rule that, wherever
many species of a genus have been formed, the species of that genus
present a number of varieties, that is of incipient species, beyond the
average. It is not that all large genera are now varying much, and are
thus increasing in the number of their species, or that no small genera
are now varying and increasing; for if this had been so, it would have
been fatal to my theory; inasmuch as geology plainly tells us that small
genera have in the lapse of time often increased greatly in size;
and that large genera have often come to their maxima, declined, and
disappeared. All that we want to show is, that where many species of a
genus have been formed, on an average many are still forming; and this
holds good.

There are other relations between the species of large genera and their
recorded varieties which deserve notice. We have seen that there is no
infallible criterion by which to distinguish species and well-marked
varieties; and in those cases i