88 PROFESSOR LANKE8TER, 



teiium, as limited by Cohn, and often exhibit active, darting 

 movements. 



The objection which is founded on the presence of colouring 

 matter in B. rubescens is easily met. The pigment of B. 

 rubescens contains neither phycocyan nor chlorophyll, and 

 one or both of these colouring-matters is present in all Pro- 

 tophyta and Thallophyta, which are not referable either to 

 the Schizomycetes, Saccharomycetes, or to the so-called Pungi. 

 On the other hand, pigmentary matter similar to Bacterio- 

 purpurin has been observed in other forms recognised as 

 Schizomycetes, and is not uncommon in various groups of 

 Fungi. It seems to me that the presence of a red colouring 

 matter in B. rubescens is a fact of no significance Avhatever, 

 as far as its relationship to other forms is concerned. In 

 considering the question of those relationships we should 

 mentally bleach B. rubescens. 



Further as to the choice of the generic term Bacterium for 

 the designation of our organism, I have this to say. From 

 the known facts as to the mode of occurrence of those 

 forms of Schizomycetes which Cohn has classed as Sphsero- 

 bacteria, Microbacteria, Desmobacteria, and Spirobacteria, 

 and from what I have been led to infer as to the connection 

 of the various forms of plastids in my red growth, I consider 

 that Ave must definitely accept what Professor Cohn himself, 

 I believe, would approve — namely, that his groups and their 

 genera are simply assemblages of forms and may include but 

 a few real species, which are represented by phases of growth 

 in each of his form-genera and form-families. 



This being the case, it becomes necessary to select generic 

 terms for the designation of the true physiological species. 

 From the widely accepted use of the term Bacterium, I am 

 led to adopt it for the generic name of all those Schizomycetes 

 ivhich under certain conditions of growth present biscuit- 

 shaped plastids capable of active locomotion. 



Accordingly I should place the red organism under con- 

 sideration in the genus Bacterium as B. rubescens, together 

 with B. lineola and B. termo. 



I am not in a position to discuss the whole question, but I 

 think it probable that Bacillus is a really distinct genus 

 and that the Spirobacteria are only form-phases of Bacterium 

 and Bacillus. 



It appears to me to be an open question whether B. termo 

 may not be a diminutive breed or specialised race of J5. 

 lineola, standing in the same relation to it as does the St. 

 Thomas' maceration-breed of B. rubescens (PI. Ill, fig. 4) to 

 its larger biscuit-shaped phase (PI. Ill, fig. 2). The con- 



