460 ‚THIRD PART.—BACTERIA OR SCHIZOMYCETES. 
sporous Bacteria; the second those which have no endogenous spore-formation, ‘the 
Arthrosporous Bacteria. It has yet to be seen whether this distinction will. be 
permanently maintained. It is evident from the gaps in our present knowledge 
that many forms are met with whose behaviour in this respect has not yet been 
ascertained. The distinction therefore is not a convenient one for a purely practical 
classification of the Bacteria. 
a. ENDOSPOROUS BACTERIA. 
The forms included under this term are chiefly known in the growth-form 
of single rods consisting of one or a few cells, or of rods joined: together and forming 
long filaments; they may also be collected together into larger gelatinous masses 
or membranes. In some forms the rods are spirally twisted, and these I name here 
Spirillum of Van Tieghem. Others do not show these curvatures, but are either 
straight or very slightly bent; all these I include under the term Bacillus and place 
under that genus all the endosporous forms which have been hitherto known either 
as Bacillus or as Clostridium, Bacteridium, Vibrio, or by some other name. All 
non-endosporous forms bearing these names on account of their growth-form are 
of course excluded from the group. ; 
The Bacteria in question are distinguished by the peculiar mode of spore- 
formation. At the commencement of the process the protoplasm of each cell 
which has hitherto been homogeneous becomes somewhat darker and in some cases 
visibly granular, and in the forms enumerated on page 455, which however are the 
smaller number, it gives the amyloid reaction. Then a darker and comparatively 
very small body makes its appearance in the interior of each:cell and soon increases 
rapidly in volume, acquiring a distinct outline some time before it reaches its ultimate 
size and becoming strongly refringent. It has now the aspect of a glistening bluish 
sharply defined dark granule, and continues to grow till it has reached its definite 
size and shape, which it does in the space of a few hours. As it enlarges, the 
surrounding protoplasm or the amyloid substance disappears, and the body when 
fully developed is surrounded only by a pellucid substance inside the very delicate 
membrane of the mother-cell; this body may be termed a spore or resting spore. 
In the great majority of observed cases one spore only is formed each time 
in a cell, The supposed exceptional case’ of two spores being formed in a single 
cell is rare, and is moreover said to occur in forms which as a rule produce only, 
one spore ; it is possible that the partition-wall between two sporogenous cells may 
have been overlooked. The sporogenous cell is according to the species either not 
different from the vegetating cells of the same species or form, or is distinguished 
by being somewhat thicker and of a different shape; the change of shape is often 
caused by the appearance of a fusiform or club-shaped enlargement at one extremity, 
in which the spore is formed. In this case the mature spore is usually much shorter 
than the mother-cell, and is seen as a glistening body in the enlarged portion of the 
parent-cell; the apparently empty part of the cell, and in some cases also sterile 

‘ Prazmowski, as cited on page 455.—E. Kern, Ueber ein Milchferment &c. (Bot. Ztg. 1882, 
p- 264, and Bull. Soc. Hist. Nat. Moscon, 1882), 
