The Character oj the Flagella 347 



2. To determine whether or not there is a difference in the 

 number or character of the flagella of the modified forms of 

 these bacteria corresponding with the variations that are found 

 to exist in their physiological and etiological manifestations. 



3. To determine the significance of the flagella in classif}'ing 

 motile bacteria, as illustrated bj- a comparative study of these 

 filaments on three typical species, representing morphol- 

 ogically three closely allied groups*, and biologically three 

 distinct groups, of bacteria. 



It was my opinion in 1891 that there was a well marked 

 specific difference in the flagella of these species, but more ex- 

 tended investigations have caused me to recede somewhat from 

 that opinion and to call attention at this time, in accordance 

 with the results of my observations, to the similarity which 

 exists between them. 



METHOD FOR STAINING THE FLAGEI,I,A. 



The difficulties which have been experienced in the demon- 

 stration of the flagella both by myself and others, necessitate 

 a somewhat careful consideration of the method which has 

 been followed in obtaining the results herein recorded. As I 

 have been unable to detect the flagella on living bacteria, my 

 descriptions apply to stained preparations only. With the ex- 

 ception of certain modifications, I^oefiler's method has been 

 followed. The advantages that are claimed for the modified 

 method over the original process are : (i) the preparations are 

 more uniformly free from a deeply stained background which 

 conceals entirely or renders indistinct the individual filaments ; 



(2) there is a better distribution of bacteria on the cover-glass ; 



(3) the application is more simple and the results more trust- 

 worthy. The majority of the changes which I have made 

 were fully described in a previous article''. The others are 

 incorporated here. The method as I have used it, is as follows : 

 the principle that is involved in staining the flagella is 

 simply the one employed in the use of a mordant or fixative. 

 The methods which have been at all successful (beyond the 

 experience of the originator) in staining the flagella require a 



* Group is here taken in a narrow sense, signifying a species and its 

 varieties only. 



