HISTORY OF OUR KNOWLEDGE OF BACTERIA. 113 



arranging the micro-organisms for reference, but 

 it may lead the investigator to work upon the same 

 lines as Zopf, and by tracing out the life-history 

 of individual forms in pure cultivations, either to 

 extend his work in establishing Protean species, 

 or to restrict the doctrine of pleomorphism to a 

 few forms. 



8 



