hat many of those vegetables and animals,
which are produced by solitary generation, gradually become more
perfect, and at length produce a sexual progeny.

A third order of organic nature consists of hermaphrodite vegetables
and animals, as in those flowers which have anthers and stigmas in the
same corol; and in many insects, as leeches, snails, and worms; and
perhaps all those reptiles which have no bones, according to the
observation of M. Poupart, who thinks, that the number of
hermaphrodite animals exceeds that of those which are divided into
sexes; Mem. de l'Acad. des Sciences. These hermaphrodite insects I
suspect _to_ be incapable of impregnating themselves for reasons
mentioned in Zoonomia, Sect. XXXIX. 6. 2.

And, lastly, the most perfect orders of animals are propagated by
sexual intercourse only; which, however, does not extend to
vegetables, as all those raised from seed produce some generations of
buds or bulbs, previous to their producing flowers, as occurs not only
in trees, but also in the annual plants. Thus three or four joints of
wheat grow upon each other, before that which produces a flower; which
joints are all separate plants growing over each other, like the buds
of trees, previous to the uppermost; though this happens in a few
months in annual plants, which requires as many years in the
successive buds of trees; as is further explained in Phytologia, Sect.
IX. 3. 1.

IV. _Conclusion._

Where climate is favourable, and salubrious food plentiful, there is
reason to believe, that the races of animals perpetually improve by
reproduction. The smallest microscopic animals become larger ones in a
short time, probably by successive reproductions, as is so distinctly
seen in the buds of seedling apple-trees, and in the bulbs of tulips
raised from seed; both which die annually, and leave behind them one
or many, which are more perfect than themselves, till they produce a
sexual progeny, or flowers. To which may be added, the rapid
improvement of our domesticated dogs, horses, rabbits, pigeons, which
improve in size, or in swiftness, or in the sagacity of the sense of
smell, or in colour, or other properties, by sexual reproduction.

The great Linneus having perceived the changes produced in the
vegetable world by sexual reproduction, has supposed that not more
than about sixty plants were at first created, and that all the others
have been formed by their solitary or sexual reproductions; and ad