“Let us now turn to the nectar-feeding insects; we may suppose the
plant, of which we have been slowly increasing the nectar by continued
selection, to be a common plant; and that certain insects depended in
main part on its nectar for food. I could give many facts showing how
anxious bees are to save time: for instance, their habit of cutting
holes and sucking the nectar at the bases of certain flowers, which with
a very little more trouble, they can enter by the mouth. Bearing such
facts in mind, it may be believed that under certain circumstances
individual differences in the curvature or length of the proboscis,
etc., too slight to be appreciated by us, might profit a bee or other
insect, so that certain individuals would be able to obtain their food
more quickly than others; and thus the communities to which they
belonged would flourish and throw off many swarms inheriting the same
peculiarities.”
Aside from the general criticism that will suggest itself here also, it
should be pointed out that even if “certain individuals” of the bees had
slightly longer proboscides, this would, in the case of the hive-bees at
least, be of no avail, since they do not reproduce, and hence leave no
descendants with longer mouth-parts. Of course, it may be replied that
those colonies in which the queens produce more of the long-proboscis
kind of worker would have an advantage over other colonies not having so
many individuals of this sort. It would then be a competition of one
colony with another, as Darwin supposes to take place in colonial forms.
But whether slight differences of this sort would lead to the
elimination of the least well-endowed colonies is entirely a matter of
speculation. Since there are flowers with corolla-tubes of all lengths,
we can readily suppose that if one kind of flower excluded individuals
of certain colonies, they would search elsewhere for their nectar rather
than perish. While different races might arise in this way, the process
would not be the survival of the fittest, but a process of adaptation to
a new environment.
We come now to a topic on which Darwin lays much stress: the divergence
of character. He tries to show how the “lesser differences between the
varieties become augmented into the greater differences between
species.”
“Mere chance, as we may call it, might cause one variety to differ in
some character from its parents, and the offspring of this variety again
to differ from its parent in the very same character and in a greater
degree; but this alone would never account for so habitual and large a
degree of difference as that between the species of the same genus. As
has always been my practice, I have sought light on this head from our
domestic productions.”
Then, after pointing out that under domestication two different races,
the race-horse and the dray-horse, for instance, might arise by
selecting different sorts of variations, Darwin inquires:—
Public-domain text, read in full here on John Shaqi.
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