Long before having arrived at this part of my work, a crowd of
difficulties will have occurred to the reader. Some of them are so
grave that to this day I can never reflect on them without being
staggered; but, to the best of my judgment, the greater number are only
apparent, and those that are real are not, I think, fatal to my theory.
These difficulties and objections may be classed under the following
heads:
Firstly, why, if species have descended from other species by
insensibly fine gradations, do we not everywhere see innumerable
transitional forms? Why is not all nature in confusion instead of the
species being, as we see them, well defined?
Secondly, is it possible that an animal having, for instance, the
structure and habits of a bat, could have been formed by the
modification of some animal with wholly different habits? Can we
believe that natural selection could produce, on the one hand, organs
of trifling importance, such as the tail of a giraffe, which serves as
a fly-flapper, and, on the other hand, organs of
such wonderful structure, as the eye, of which we hardly as yet fully
understand the inimitable perfection?
Thirdly, can instincts be acquired and modified through natural
selection? What shall we say to so marvellous an instinct as that which
leads the bee to make cells, which have practically anticipated the
discoveries of profound mathematicians?
Fourthly, how can we account for species, when crossed, being sterile
and producing sterile offspring, whereas, when varieties are crossed,
their fertility is unimpaired?
The two first heads shall be here discussed Instinct and Hybridism in
separate chapters.
_On the absence or rarity of transitional varieties._ As natural
selection acts solely by the preservation of profitable modifications,
each new form will tend in a fully-stocked country to take the place
of, and finally to exterminate, its own less improved parent or other
less-favoured forms with which it comes into competition. Thus
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