460 THIRD PART. BACTERIA OR SCHIZOMFCETES. 



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. ENDOS^OROUS 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 l 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 



1 Prazmowski, as cited on page 455. E. Kem, Ueber ein Milchferment &c. (Bot. Ztg. 1882, 

 p. 264, and Bull. Soc. Hist. Nat. Moscou, 1882). 



