vations. Watching meat during its passage
from freshness to decay, prior to the appearance of maggots he
invariably observed flies buzzing round the meat and frequently
alighting on it. The maggots, he thought, might be the half-developed
progeny of these flies.

The inductive guess precedes experiment, by which, however, it must be
finally tested. Redi knew this, and acted accordingly. Placing fresh
meat in a jar and covering the mouth with paper, he found that, though
the meat putrefied in the ordinary way, it never bred maggots, while
the same meat placed in open jars soon swarmed with these organisms.
For the paper cover he then substituted fine gauze, through which the
odour of the meat could rise. Over it the flies buzzed, and on it
they laid their eggs, but, the meshes being too small to permit the
eggs to fall through, no maggots were generated in the meat. They
were, on the contrary, hatched upon the gauze. By a series of such
experiments Redi destroyed the belief in the spontaneous generation of
maggots in meat, and with it doubtless many related beliefs. The
combat was continued by Vallisneri, Schwammerdam, and Reaumur, who
succeeded in banishing the notion of spontaneous generation from the
scientific minds of their day. Indeed, as regards such complex
organisms as those which formed the subject of their researches, the
notion was banished for ever.

But the discovery and improvement of the microscope, though giving a
death-blow to much that had been previously written and believed
regarding spontaneous generation, brought also into view a world of
life formed of individuals so minute--so close as it seemed to the
ultimate particles of matter--as to suggest an easy passage from atoms
to organisms. Animal and vegetable infusions exposed to the air were
found clouded and crowded with creatures far beyond the reach of
unaided vision, but perfectly visible to an eye strengthened by the
microscope. With reference to their origin these organisms were
called 'Infusoria. Stagnant pools were found full of them, and the
obvious difficulty of assigning a germinal origin to existences so
minute furnished the precise condition necessary to give new play to
the notion of heterogenesis or spontaneous generation.

The scientific world was soon divided into two hostile camps, the
leaders of which only can here be briefly alluded to. On the one
side, we have Buffon and Needham, the former postulating his 'orga