BACTERIAL CLASSIFICATION 9 



appeared, some colorless and some red. No inter- 

 mediate grades were observed and cultures isolated 

 from colorless and red colonies bred true to their 

 respective types, altho the acid-forming mutation could 

 always be obtained from old white colonies. In other 

 cultural characters and in serum reactions fermenting 

 and non-fermenting types were identical. In the dis- 

 cussion of Neisser's paper Schottelius, Kruse, Gruber, 

 and Gotschlich reported observations of similar bac- 

 terial variations. 



Slight fluctuating variations are on the other hand 

 familiar to all bacteriologists who have examined, with 

 care, sub-cultures from one parent strain. Conn (1900) 

 and Sullivan (1905) studied color variations of this sort. 

 On plates sown from a single colony they observed 

 daughter colonies varying appreciably in shade, and by 

 selecting extreme forms and repeating the process they 

 were able ultimately to obtain quite distinct types. 

 Ruzicka (1899) describes the modification of a fluo- 

 rescent water bacillus into a type resembling B. pyo- 

 cyaneus by the selection of slight variations. 



Whether sudden mutation, or gradual transformation 

 of minor fluctuations, be the more important factor in 

 the production of differing bacterial types, is still unsettled. 

 It must be considered an open question indeed among 

 the higher forms as well. It is sufficient in the present 

 connection to note that variations of both sorts exist, 

 as well as some which are hard to place definitely in 



