which have
probably been originally mule-productions; nor could any kind of
improvement or change have happened to them, except by the difference of
soil or climate.

3. I conclude, that the imagination of the male at the time of copulation,
or at the time of the secretion of the semen, may so affect this secretion
by irritative or sensitive association, as described in No. 5. 1. of this
section, as to cause the production of similarity of form and of features,
with the distinction of sex; as the motions of the chissel of the turner
imitate or correspond with those of the ideas of the artist. It is not here
to be understood, that the first living fibre, which is to form an animal,
is produced with any similarity of form to the future animal; but with
propensities, or appetences, which shall produce by accretion of parts the
similarity of form, feature, or sex, corresponding to the imagination of
the father.

Our ideas are movements of the nerves of sense, as of the optic nerve in
recollecting visible ideas, suppose of a triangular piece of ivory. The
fine moving fibres of the retina act in a manner to which I give the name
of white; and this action is confined to a defined part of it; to which
figure I give the name of triangle. And it is a preceding pleasurable
sensation existing in my mind, which occasions me to produce this
particular motion of the retina, when no triangle is present. Now it is
probable, that the acting fibres of the ultimate terminations of the
secreting apertures of the vessels of the testes, are as fine as those of
the retina; and that they are liable to be thrown into that peculiar
action, which marks the sex of the secreted embryon, by sympathy with the
pleasurable motions of the nerves of vision or of touch; that is, with
certain ideas of imagination. From hence it would appear, that the world
has long been mistaken in ascribing great power to the imagination of the
female, whereas from this account of it, the real power of imagination, in
the act of generation, belongs solely to the male. See Sect. XII. 3. 3.

It may be objected to this theory, that a man may be supposed to have in
his mind, the idea of the form and features of the female, rather than his
own, and therefore there should be a greater number of female births. On
the contrary, the general idea of our own form occurs to every one almost
perpetually, and is termed consciousness of our existence, and thus may
effect, that the num