CLASSIFICATION AND DESCRIPTION OF SPECIES. 483 



bacterium or a bacillus. To meet this dith'culty a nmi:li-:md 

 ready rule was suggested viz., that a rod le>s than t \\ic-- 

 ln-eadth in length should be considered as a bacterium, and <>tli--r 

 \vi>e a bacillus. But this purely arbitrary division was inadequate, 

 from the fact that a rod at one stage of its growth or under certain 

 conditions might, as far as length went, truly be a bacterium, and 

 under other circumstances be of such a length as to entitle its Innng 

 considered a bacillus (Fig. 197). We should avoid such contusion 

 if we followed Zopf, and acknowledged as a difference U-tween a 

 bacterium and a bacillus the presence or absence of that form of 

 spore- for mat ion now distinguished as endogenous spore-formation. 

 We might then conveniently retain this generic term, to include 

 that group of rod-forms in which this spore-formation is as yet 



FIG. 197. FRIEDLANDKH'S PNKIMOCOOTS, x 1500 



unknown; moreover, we should, by so doing, with one or two 

 exceptions, collect together those short rod-forms which appe. 

 link the simple cocci to the spore-bearing rods or Ixu-ill 



The grouping together of the different specie aocordi 

 character of the colonies in nutrient gelatine is also of quest 



r 



a slignt variation i. - i At the name 



considerably affect the appearances of the colonies. 



case of the comma-bacilli of Finkler and of K 



