ith each other, and are believed not to
be able to impregnate themselves; which belongs, therefore, to sexual
generation, and not to the solitary reproduction of which I am now
speaking.

As in the chemical production of any new combination of matter, two
kinds of particles appear to be necessary; one of which must possess
the power of attraction, and the other the aptitude to be attracted,
as a magnet and a piece of iron; so in vegetable or animal
combinations, whether for the purpose of nutrition or for
reproduction, there must exist also two kinds of organic matter; one
possessing the appetency to unite, and the other the propensity to be
united; (see Zoonomia, octavo edition, Sect. XXXIX. 8.) Hence in the
generation of the buds of trees, there are probably two kinds of
glands, which acquire from the vegetable blood, and deposite beneath
the cuticle of the tree two kinds of formative organic matter, which
unite and form parts of the new vegetable embryon; which again uniting
with other such organizations form the caudex, or the plumula, or the
radicle, of a new vegetable bud.

A similar mode of reproduction by the secretion of two kinds of
organic particles from the blood, and by depositing them either
internally as in the vernal and summer aphis or volvox, or externally
as in the polypus and taenia, probably obtains in those animals; which
are thence propagated by the father only, not requiring a cradle, or
nutriment, or oxygenation from a mother; and that the five
generations, said to be seen in the transparent volvox globator within
each other, are perhaps the successive progeny to be delivered at
different periods of time from the father, and erroneously supposed to
be mothers impregnated before their nativity.

II. Sexual as well as solitary reproduction appears to be effected by
two kinds of glands; one of which collects or secretes from the blood
formative organic particles with appetencies to unite, and the other
formative organic particles with propensities to be united. These
probably undergo some change by a kind of digestion in their
respective glands; but could not otherwise unite previously in the
mass of blood from its perpetual motion.

The first mode of sexual reproduction seems to have been by the
formation of males into hermaphrodites; that is, when the numerous
formative glands, which existed in the caudex of the bud of a tree, or
on the surface of a polypus, became so united as to form but