rly useless to the community for any other purpose, and which are
ultimately slaughtered by their industrious and sterile sisters? It may
be difficult, but we ought to admire the savage instinctive hatred
of the queen-bee, which urges her to destroy the young queens, her
daughters, as soon as they are born, or to perish herself in the combat;
for undoubtedly this is for the good of the community; and maternal love
or maternal hatred, though the latter fortunately is most rare, is all
the same to the inexorable principles of natural selection. If we admire
the several ingenious contrivances by which orchids and many other
plants are fertilised through insect agency, can we consider as equally
perfect the elaboration of dense clouds of pollen by our fir-trees, so
that a few granules may be wafted by chance on to the ovules?

SUMMARY: THE LAW OF UNITY OF TYPE AND OF THE CONDITIONS OF EXISTENCE
EMBRACED BY THE THEORY OF NATURAL SELECTION.

We have in this chapter discussed some of the difficulties and
objections which may be urged against the theory. Many of them are
serious; but I think that in the discussion light has been thrown on
several facts, which on the belief of independent acts of creation are
utterly obscure. We have seen that species at any one period are not
indefinitely variable, and are not linked together by a multitude of
intermediate gradations, partly because the process of natural selection
is always very slow, and at any one time acts only on a few forms;
and partly because the very process of natural selection implies the
continual supplanting and extinction of preceding and intermediate
gradations. Closely allied species, now living on a continuous area,
must often have been formed when the area was not continuous, and when
the conditions of life did not insensibly graduate away from one part to
another. When two varieties are formed in two districts of a continuous
area, an intermediate variety will often be formed, fitted for an
intermediate zone; but from reasons assigned, the intermediate variety
will usually exist in lesser numbers than the two forms which it
connects; consequently the two latter, during the course of further
modification, from existing in greater numbers, will have a great
advantage over the less numerous intermediate variety, and will thus
generally succeed in supplanting and exterminating it.

We have seen in this chapter how cautious we should be in concluding
that the mos