24 BACTERIOLOGY. 



duced spores, were in the first instance mat- 

 ters that were regarded with indifference. 



In order to determine truly natural genera 

 and species, more must be known than the sup- 

 posed " typical," " constantly recurring," or 

 " principal " forms. Something additional has 

 been obtained through our knowledge of flag- 

 ella. (Fig 12.) Many cells without membranes, 

 such as amoebae, have, as is well known, the 

 power of sending out protoplasmic processes 

 quite at will, as in the so-called pseudopodia. 

 The term cilium or flagellum is used in a more 

 restricted sense than pseudopodium, and is ap- 

 plied to the delicate threads of protoplasm which 

 are extended through definite openings in the 

 cell membrane and which retain a connection 

 with the cell-contents. The flagella of bacteria, 

 which were discovered by Ehrenberg, are now 

 known to be appendages of the membrane, 

 and their connection with the cell proto- 

 plasm has not been accurately determined ; they 

 seem, however, to be true organs of locomotion. 

 The possession of cilia brings bacteria into 

 closer -relation with the groups of monads and 

 flagellates, organisms which are regarded as ani- 

 mals. A. Fischer has attempted to make use 

 of the flagella for purposes of diagnosis. He 

 lays stress upon the presence or absence of these 

 structures, and their occurrence singly or in 



