HISTORY OF OUR KNOWLEDGE OF BACTERIA. Ill 



genera or species. The mode of reproduction is 

 not sufficiently known to afford a better means for 

 distinction than the other morphological appear- 

 ancestaken alone ; nor can we depend upon phy- 

 siological action, which is held by many to vary 

 with the change of form, according to altered 

 surroundings. 



Zopf, who has warmly supported the pleomor- 

 phisvi of bacteria, has suggested as a result of 

 his investigations a division of the Schizomycetes, 

 Spaltpilze, or Fission-fungi, into the following four 

 groups : * 



1. Coccaceae. Possessing (so far as our knowledge 

 at present reaches) only cocci, and thread forms resulting 

 from the juxtaposition of cocci. The fission occurs in one 

 or more directions. 



Genera : Streptococcus, Micrococcus, Merismopedia, 

 Sarcina. 



2. Bacteriacese. Possessing mostly cocci, rods 

 (straight or bent), and thread-forms (straight or spiral) 

 The first may be absent, and the last possess no distinction 

 between base and apex. 



Division (as far as is known) occurs only in one 

 direction. 



Genera: Bacterium, Spirillum, Vibrio, Leuconostoc, 

 Bacillus, Clostridium. 



3. Leptotrichese. Possessing cocci, rods, and 

 thread-forms (which show a distinction between base and 

 apex). The last straight or spiral. 



* Zopf, Die Spaltyilze, 1885. 



