flies away from actual contact with the meat. The meat putrified as
usual, but did not breed maggots; while the same kind of meat exposed
in open jars swarmed with them. He next placed some meat in a jar with
some wire gauze over the top. The flies were attracted by the smell of
the meat as usual, but could not reach the meat. Instead they laid their
eggs upon the gauze, where they hatched in due time, while no maggots
were generated in the meat. Thus from this time onward it became
gradually understood that, at least in the case of all the larger and
higher forms of life, Harvey's dictum, as announced some years
previously, was true, and that life comes only from life.

But the invention of the microscope opened the way for a renewal of the
controversy regarding the origin of life. Bacteria were discovered in
1683; and it was soon observed that no precautions with screens or other
stoppers could prevent bacteria and other low organisms from breeding in
myriads in every kind of organic matter. Here apparently was an entirely
new foundation for the doctrine of spontaneous generation. It was freely
admitted that all the higher forms of life arise only by process of
natural generation from others of their own kind; but did not these
microscopic organisms prove that there was "a perpetual abiogenetic
fount by which the first steps in the evolution of living organisms
continued to arise, under suitable conditions, from inorganic
matter"?[9]

[Footnote 9: Encyclopaedia Britannica, Vol. I, p. 64.]

The famous "barnacle-geese" ought not to be omitted from any sketch of
the vicissitudes of this doctrine of Biogenesis. An elaborate
illustrated account covering their alleged natural history was printed
in one of the early volumes of the Royal Society of London. Buds of a
particular tree growing near the sea were described as producing
barnacles, and these falling into the water were alleged to be
transmuted into geese. Nor should we omit mention of Huxley's _Bathybius
Haeckelii_, a slimy substance supposed to exist in great masses in the
depths of the ocean and to consist of undifferentiated protoplasm, the
exhaustless fountain from which all other forms of life had been
derived. Not long after Huxley had given it a formal scientific name in
1868, it was discovered to be merely a precipitate of gypsum thrown down
from sea water by alcohol, and thus a product of clumsy manipulation in
the laboratory, instead of a natural product