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MORPHOLOGY AND BIOLOGY OF BACTLRLl. 7

and con, but which wo cannot discuss here. SuiEce it to sav,
that at present the great mass of evidence points to the conchi-
sion that such transformations cannot be brought about in tlje
manner indicated. On the other hand, there are many kinds
of bacteria that manifest two or all of the fundamental forms
at the same time. These have been designated as pleomorphous,
in contradistinction to those which produce only one form
(monomorphous). (See Zopf.)
The following forms arc classed by Zopf* and others among
the bacteria ; Fliigge speaks of them as being of doubtful rela-
tion to the bacteria, while Cornil and Babes ^ make of some of
them a sort of connecting link between the bacteria and infu-
soria :
-C Monados : large, spherical, oval, or short cylindrical cells,
provided with cilia, often in pairs (Fig. 1, ni).
2. Rhabdoraonas : large spindle-shaped ciliated cells (Fig. 1, $).
3. Spiromonas : leaf-like, flat cells, " twisted around an imag-
inary axis in the direction of their length."

2. Cumulative Forms of Bacteria.
Besides these forms of the single cells, we recognize various
confio-urations which result from the accumulation or combi-
nation of several cells. These are :
Thread-forms or Chain-forms : i.e. forms produced by a suc-
X.
cession of single cells. To these belong :
a. Streptococci (Chain-cocci) : cocci which appear chiefly
in chains, sometimes improperly called Torula (Fig. 1, cI).
b. Leptothrix : long, articulated threads, composed of single
cells (cocci or rods), (Fig. 1, r').
2. Cluster-forms, i.e. groups, produced by the aggregation of
*
cells without definite arrangement, particularly Staphylococci,'
which are mostly found in clusters (Fig. 1, c).
3. Surface- or Mass-forms, which are produced by fissation in
two or three directions, such as merismopedia: plate-shaped
colonies, produced bv fissation in two directions (Fi g. 1, c), and

*aTa^v'kri, A. clus'er of grapf^s