or the hay are not dead, but are ready to manifest their
vitality as soon as the bovine or herbaceous shrouds in which they are
imprisoned are rent by the macerating action of water. The hypothesis
therefore must be classified under Xenogenesis, rather than under
Abiogenesis. Such as it was, I think it will appear, to those who will be
just enough to remember that it was propounded before the birth of modern
chemistry, and of the modern optical arts, to be a most ingenious and
suggestive speculation.

But the great tragedy of Science--the slaying of a beautiful hypothesis
by an ugly fact--which is so constantly being enacted under the eyes of
philosophers, was played, almost immediately, for the benefit of Buffon
and Needham.

Once more, an Italian, the Abbe Spallanzani, a worthy successor and
representative of Redi in his acuteness, his ingenuity, and his learning,
subjected the experiments and the conclusions of Needham to a searching
criticism. It might be true that Needham's experiments yielded results
such as he had described, but did they bear out his arguments? Was it not
possible, in the first place, he had not completely excluded the air by
his corks and mastic? And was it not possible, in the second place, that
he had not sufficiently heated his infusions and the superjacent air?
Spallanzani joined issue with the English naturalist on both these pleas,
and he showed that if, in the first place, the glass vessels in which the
infusions were contained were hermetically sealed by fusing their necks,
and if, in the second place, they were exposed to the temperature of
boiling water for three-quarters of an hour,[8] no animalcules ever made
their appearance within them. It must be admitted that the experiments
and arguments of Spallanzani furnish a complete and a crushing reply to
those of Needham. But we all too often forget that it is one thing to
refute a proposition, and another to prove the truth of a doctrine which,
implicitly or explicitly, contradicts that proposition; and the advance
of science soon showed that though Needham might be quite wrong, it did
not follow that Spallanzani was quite right.

[Footnote 8: See Spallanzani, _Opere_, vi. pp. 42 and 51.]

Modern Chemistry, the birth of the latter half of the eighteenth century,
grew apace, and soon found herself face to face with the great problems
which biology had vainly tried to attack without her help. The discovery
of oxygen led to the laying o