only that in

certain of these cases development is spontaneous, and in others is
not independent of the male; and the method of proceeding in regard to
these matters will set forth by and by, for the method is somewhat
like to the method followed in the case of birds. But whensoever
creatures are spontaneously generated, either in other animals, in the
soil, or on plants, or in the parts of these, and when such are
generated male and female, then from the copulation of such
spontaneously generated males and females there is generated a
something-a something never identical in shape with the parents, but a
something imperfect. For instance, the issue of copulation in lice
is nits; in flies, grubs; in fleas, grubs egg-like in shape; and
from these issues the parent-species is never reproduced, nor is any
animal produced at all, but the like nondescripts only.