average age of a human being to be thirty years, and the population of
the world at that time to be 1000 millions. And the famous Haller
maintained all this nonsense, in spite of its ridiculous consequences,
even after Wolff had discovered the real course of embryonic
development and established it by direct observation!

Among the philosophers of the time the distinguished Leibnitz was the
chief defender of the "preformation theory," and by his authority and
literary prestige won many adherents to it. Supported by his system of
monads, according to which body and soul are united in inseparable
association and by their union form the individual, or the "monad,"
Leibnitz consistently extended the "scatulation theory" to the soul,
and held that this was no more evolved than the body. He says, for
instance, in his Theodicee: "I mean that these souls, which one day
are to be the souls of men, are present in the seed, like those of
other species; in such wise that they existed in our ancestors as far
back as Adam, or from the beginning of the world, in the forms of
organised bodies."

The theory seemed to receive considerable support from the
observations of one of its most zealous supporters, Bonnet. In 1745 he
discovered, in the plant-louse, a case of parthenogenesis, or
virgin-birth, an interesting form of reproduction that has lately been
found by Siebold and others among various classes of the articulata,
especially crustacea and insects. Among these and other animals of
certain lower species the female may reproduce for several generations
without having been fertilised by the male. These ova that do not need
fertilisation are called "false ova," pseudova or spores. Bonnet saw
that a female plant-louse, which he had kept in cloistral isolation,
and rigidly removed from contact with males, had on the eleventh day