ON A rEACH-COLOURED BACTERIUM. S3 



Macroplasts or Reproductive Discs. — The form of plastid 

 which I have now to describe is one of altogether special 

 interest, since it seems possible that we have in it a definite 

 reproductive form, whilst the phenomena of division pre- 

 sented by it, resulting in the formation of new colonies of 

 plastids, are so exceptional as to be in themselves a matter 

 of interest from the point of view of the histologist. At the 

 same time, should it be found that the colourless Bacteria 

 develop reproductive discs, or macroplasts of the same charac- 

 ter as those of B. rubescens, we shall have ascertained a pos- 

 sible source of origin for those excessively minute germs 

 wliich are so widely distributed, and which so readily 

 develop in putrescible liquids. 



In the jar of fresh water in which my Bacterium rubescens 

 originally developed the growth was continually kept up by 

 the addition on my part of dead animal matter, such, for 

 instance, as an earthworm or a moth, or a limb of a crayfish. 

 After luxuriating for a time, the red growth would always 

 languish and become reduced to a small area, varying in 

 colour from peach colour to brick red, and this film would 

 lie at the bottom of the vessel beneath the black deposit of 

 carbonised debris. When it had assumed this state I found 

 that I could always call forth an abundant croj) by the addi- 

 tion of fresh animal matter. In September of 1873 the 

 growth had been allowed to dwindle to its very smallest 

 limits, and I then examined some of the very deeply coloured 

 film which lay at the bottom of the glass jar, and was 

 visible by inspection from below. I found it to consist of 

 a felted mass of green unicellular algse, desmids, various 

 organic filaments, and a large quantity of gloeogenous plas- 

 ties of Bacterium rubescens, some in the condition of sheets 

 free from any excess of gelatinous matrix, and forming 

 very highly coloured expanses. Such mycoderma-like frag- 

 ments (but of much larger extent) as those drawn in Plate III, 

 fig. 10 and fig. 22, were abundant, agreeing in the cavernous 

 shape of the aggregate or frond with the Clathrocystis of 

 Henfrey.^ The most remarkable appearances, however, were 

 a large number of disc-like bodies, of very various size, 

 deeply impregnated with the red colour, distinguished as 

 Bacterio-purpurin. These bodies varied in size from the 

 dimensions of an ordinary biscuit-shaped plastid of B. ru- 

 bescens to that of a circle with y^oth inch diameter. The 



' I am informed by Professor Ferdinand Cohn that be bas referred tbis 

 form of B. rubescens to Henfrey's genus as Clathrocystis rubeo-persicinus. 

 He also considers some of the forms of my B. rubescens to be the Monas 

 Okeni of Ebrenberg. 



VOL. XVI. NEW SER. C 



