72 SULPHUR BACTERIA 



duals of varied size, a fact which makes it practically impossible 

 to fix upon a certain defmite size as being an attribute of any 

 particular organism. The method adopted by Winogradsky 

 in his study of Beggiatoa alba is not one which is justified in 

 the subdivision of bacteria. When lie found various sizes 

 of that organism in the same field connected together by 

 numerous gradations, he arbitrarily selected a particular 

 range, and bestowed upon the individuals within that range 

 a specific name. In this way several " species " of the genus 

 Beggiatoa were established by him. Such " species " are not 

 of the nature of " microspecies " or " elementary species " or 

 " pure lines." The variations in size appear to be the 

 ordinary manifestation of every culture of Beggiatoa; it is an 

 aspect in the pleomorphic tendency of this species, and no 

 more significance is to be attached to tlie variation than 

 to the variation in the number of sulphur granules in the 

 different individuals. W inogradsky established the following 

 " species " : — 



Threads up to i/x thick, Beggiatoa minima. 

 1— 2-5/A ,, ,, media. 



2-5— 4/x ,, ,, alba. 



4—5-5/^ :, ,, major. 



The figures were arbitrarily chosen by him and he admits 

 that any others would have done " weil sie nur auf Convention 

 beruht." In other words, they are intended merely as catalogue 

 names, and in that case it is not correct to label them as 

 "species." Suppose a culture of this genus in, say America, 

 shows sizes of filaments varying in thickness from, let us 

 suppose, i/Lt to 6jLt, and a culture of the same genus, in say 

 Germany, gives a crop of threads of thicknesses varying from 

 ■|/i, to 5/x. According to this " Convention " all the threads in 

 both cultures between ijx and 2-5jLt must be labelled Beggiatoa 

 media. Whilst there is still some ambiguity in the meaning 

 of the term species all must agree that it connotes a unit that 

 is sharply separated from other units, whether the bond of 

 union is known or unknown. It is more reasonable to fix 

 the name Beggiatoa alba (chosen for priority) for all thicknesses 



