ylo-dextrin) which turns
brown with iodine has been observed. Oil and fat drops have also been shown
to occur, and in the sulphur-bacteria numerous fine granules of sulphur.

[Sidenote: Nucleus.]

The question of the existence of a nucleus in the bacteria is one that has
led to much discussion and is a problem of some difficulty. In the majority
of forms it has not hitherto been possible to demonstrate a nucleus of the
type which is so characteristic of the higher plants. Attention has
accordingly been directed to the deeply-staining granules mentioned above,
and the term chromatin-granules has been applied to them, and they have
been considered to represent a rudimentary nucleus. That these granules
consist of a material similar to the chromatin of the nucleus of higher
forms is very doubtful, and the comparison with the nucleus of more highly
organized cells rests on a very slender basis. The most recent works
(Vejdovsky, Mencl), however, appear to show that nuclei of a structure and
mode of division almost typical are to be found in some of the largest
bacteria. It is possible that a similar structure has been overlooked or is
invisible in other forms owing to their small size, and that there may be
another type of nucleus--the diffuse nucleus--such as Schaudinn believed to
be the case in _B. butschlii_. Many bacteria when suspended in a fluid
exhibit a power of independent movement which is, of course, quite distinct
from the Brownian movement--a non-vital phenomenon common to all
finely-divided particles suspended in a fluid. Independent movement is
effected by special motile organs, the cilia or flagella. These structures
are invisible, with ordinary illumination in living cells or unstained
preparations, and can only be made clearly visible by special methods of
preparation and staining first used by Loeffler. By these methods the cilia
are seen to be fine protoplasmic outgrowths of the cell (fig. 1) of the
same nature as those of the zoospores and antherozoids of algae, mosses,
&c. [Sidenote: Cilia.] These cilia appear to be attached to the cell-wall,
being unaffected by plasmolysis, but Fischer states that they really are
derived from the central protoplasm and pass through minute pores in the
wall. The cilia may be present during a short period only in the life of a
Schizomycete, and their number may vary according to the medium on which
the organism is growing. Nevertheless, there is more or less constancy in