i6 , SULPHUR BACTERIA 



of observation is described on page 53. The organism under 

 observation is confined between glass slide and coverslip, and 

 treated with HgS at appropriate intervals (he held that the 

 introduction of organic matter was not necessary). When 

 under these artificial conditions the one phase of growth 

 under observation did not develop into some diflferent develop- 

 mental phase, he concluded in efi^ect that the transformation 

 was not possible under any combination of circumstances 

 under natural conditions. He held that two phases of growth 

 belonged to one and the same species, provided that it was 

 possible by a continuous-observation experiment to effect the 

 transformation of the one into the other. When he failed to 

 accomplish this, the different phases of growth were to be 

 adjudged as belonging to different species. On the strength 

 of the negative results obtained in this way Winogradsky 

 discounted the positive information obtained by the earlier 

 investigators ; and he felt justified in consequence in launching 

 a number of new genera and species, as each phase of growth 

 observed by him was regarded as a separate organism. Of 

 the numerous genera and species which are recorded by him 

 we know practically nothing of the developmental history. 

 As we know also practically nothing of their internal struc- 

 ture, or their methods of reproduction, it must be held that 

 Winogradsky's contributions have added somewhat to the 

 difficulties of subsequent investigations into the morphology 

 of the sulphur bacteria. 



It was inevitable that the attention given to Winogradsky's 

 investigations should have obscured the evidence for pleo- 

 morphism obtained by the earlier writers ; for the greater 

 part new organisms have been described after observation 

 under only one set of circumstances, and their pleomorphic 

 possibilities have seldom been considered. It has inevitably 

 followed that comparatively large numbers of new organisms 

 have appeared, and have been labelled without adequate 

 study of their structure, their developmental history, or their 

 methods of reproduction. The consequences which have 

 followed this attitude when applied to the classification of 

 the sulphur bacteria have been unfortunate, and will be 

 described in later pages. 



