[Footnote 2: 1 Corinthians xv. 36.]

The proposition that life may, and does, proceed from that which has no
life, then, was held alike by the philosophers, the poets, and the
people, of the most enlightened nations, eighteen hundred years ago; and
it remained the accepted doctrine of learned and unlearned Europe,
through the Middle Ages, down even to the seventeenth century.

It is commonly counted among the many merits of our great countryman,
Harvey, that he was the first to declare the opposition of fact to
venerable authority in this, as in other matters; but I can discover no
justification for this widespread notion. After careful search through
the "Exercitationes de Generatione," the most that appears clear to me
is, that Harvey believed all animals and plants to spring from what he
terms a "_primordium vegetale_," a phrase which may nowadays be rendered
"a vegetative germ"; and this, he says, is _"oviforme_," or "egg-like";
not, he is careful to add, that it necessarily has the shape of an egg,
but because it has the constitution and nature of one. That this
"_primordium oviforme_" must needs, in all cases, proceed from a living
parent is nowhere expressly maintained by Harvey, though such an opinion
may be thought to be implied in one or two passages; while, on the other
hand, he does, more than once, use language which is consistent only with
a full belief in spontaneous or equivocal generation.[3] In fact, the
main concern of Harvey's wonderful little treatise is not with
generation, in the physiological sense, at all, but with development; and
his great object is the establishment of the doctrine of epigenesis.

[Footnote 3: See the following passage in Exercitatio I.:--"Item _sponte
nascentia_ dicuntur; non quod ex _putredine_ oriunda sint, sed quod casu,
naturae sponte, et aequivoca (ut aiunt) generatione, a parentibus sui
dissimilibus proveniant." Again, in _De Uteri Membranis:_--"In cunctorum
viventium generatione (sicut diximus) hoc solenne est, ut ortum ducunt a
_primordio_ aliquo, quod tum materiam tum elficiendi potestatem in se
habet: sitque, adeo id, ex quo et a quo quicquid nascitur, ortum suum
ducat. Tale primordium in animalibus (_sive ab aliis generantibus
proveniant, sive sponte, aut ex putredine nascentur_) est humor in
tunica, aliquaaut putami ne conclusus." Compare also what Redi has to say
respecting Harvey's opinions, _Esperienze_, p. 11.]

The first distinct enunciation of the hypot