place in the organic world is reduced to a small one
systematically. They do not form a class by themselves, but are
simply a subclass, or even a family, and a family closely related
to several other common plants. But the absence of chlorophyll and
the resulting peculiar life has brought about a curious anomaly.
Whereas their closest allies are known only to botanists, and are
of no interest outside of their systematic relations, the bacteria
are familiar to every one, and are demanding the life attention of
hundreds of investigators. It is their absence of chlorophyll and
their consequent dependence upon complex foods which has produced
this anomaly.

CLASSIFICATION OF BACTERIA.

While it has generally been recognised that bacteria are plants,
any further classification has proved a matter of great
difficulty, and bacteriologists find it extremely difficult to
devise means of distinguishing species. Their extreme simplicity
makes it no easy matter to find points by which any species can be
recognised. But in spite of their similarity, there is no doubt
that many different species exist. Bacteria which appear to be
almost identical, under the microscope prove to have entirely
different properties, and must therefore be regarded as distinct
species. But how to distinguish them has been a puzzle.
Microscopists have come to look upon the differences in shape,
multiplication, and formation of spores as furnishing data
sufficient to enable them to divide the bacteria into genera. The
genus Bacillus, for instance, is the name given to all rod-shaped
bacteria which form endogenous spores, etc. But to distinguish
smaller subdivisions it has been found necessary to fall back upon