roup of
Myxobacteriaceae suggests a relationship with the Myxomycetes. The
existence of ciliated micrococci together with the formation of
endospores--structures not known in the Cyanophyceae--reminds us of the
flagellate Protozoa, _e.g._ _Monas_, _Chromulina_. Resemblances also exist
between the endospores and the spore-formations in the Saccharomycetes, and
if _Bacillus inflatus_, _B. ventriculus_, &c., really form more than one
spore in the cell, these analogies are strengthened. Schizomycetes such as
_Clostridium_, _Plectridium_, &c., where the sporiferous cells enlarge,
bear out the same argument, and we must not forget that there are extremely
minute "yeasts," easily mistaken for Micrococci, and that yeasts
occasionally form only one spore in the cell.

Nor must we overlook the possibility that the endospore-formation in
non-motile bacteria more than merely resembles the development of
azygospores in the Conjugatae, and some Ulothricaceae, if reduced in size,
would resemble them. Meyer regards them as chlamydospores, and Klebs as
"carpospores" or possibly chlamydospores similar to the endospores of
yeast. [v.03 p.0157] The former also looks on the ordinary disjointing
bacterial cell as an oidium, and it must be admitted that since Brefeld's
discovery of the frequency of minute oidia and chlamydospores among the
fungi, the probability that some so-called bacteria--and this applies
especially to the branching forms accepted by some bacteriologists--are
merely reduced fungi is increased. Even the curious one-sided growth of
certain species which form sheaths and stalks--_e.g._ _Bacterium
vermiforme_, _B. pediculatum_--can be matched by Algae such as _Oocardium_,
_Hydrurus_, and some Diatoms. It is clear then that the bacteria are very
possibly a heterogeneous group, and in the present state of our knowledge
their phylogeny must be considered as very doubtful.

Nearly all bacteria, owing to the absence of chlorophyll, are saprophytic
or parasitic forms. Most of them are colourless, but a few secrete
colouring matters other than chlorophyll. In size their cells are commonly
about 0.001 mm. (1 micromillimetre or 1 [micron]) in diameter, and from two
to five times that length, but smaller ones and a few larger ones are
known. Some of the shapes assumed by the cells are shown in fig. 1.

[Illustration: FIG. 1.--Preparations showing various forms of bacteria and
the various types of cilia and their arrangement.

A. _Bac