ON A PEACH-COLOURED BACTERTUM. 27 



Further Observations 07i a Peach- or Red-coloured 

 Bacterium — Bacterium ruhescens. By E. Ray Lan- 

 KESTER, M.A., r.R.S. (With Plate III.) 



The growth varying in colour from peach-blue to a ruby- 

 red which 1 described in this Journal in 1873 (vol. xiii, page 

 408, Plates XXII, XXIII) has been under my observation 

 from time to time during the last two years, and I have 

 ascertained a variety of new facts with regard to it Avhich 

 add very much to its interest. 



Frequency of Occurrence. — I have had no difficulty in ob- 

 taining any quantity of the red growth formed by B. ruhes- 

 cens ; it is probably familiar to most microscopists who 

 occupy themselves with the lower organisms of fresh Avaters. 

 Almost any mixture of Algee and Infusoria which is allowed 

 slowly to putrefy becomes the seat of its development — 

 thick, red-coloured crusts forming on the sides and bottom 

 of the jar in which the putrefaction is proceeding, and 

 resembling the coloured films which form on the sides of 

 a bottle of Burgundy Avine. 



I have received a particular form of this growth (of which 

 more below) from my friend, Mr. Charles Stewart, P.L.S., 

 of St. Thomas' Hospital, who finds it in large quantities in 

 the macerating tubs Avhicli he uses for the preparation of 

 skeletons. 



Further, from my friend, Mr. Archer, F.R.S., of Dublin, 

 I have received other samples taken in a pond fifty miles 

 distant from Dublin, which I do not feel any doubt are to 

 be considered as growths of Bacterium riibescens. To these 

 also I shall allude further below. 



Lastly, I am very much disposed to believe that the pink- 

 coloured Spirillum, described by Dr. Klein in the October 

 number of this Journal for the year 1875, is a s^^irillar phase 

 of Bacterium ruhescens. Dr. Klein Avas good enough to 

 shoAv me his specimens, and I base my opinion on a micro- 

 scopical examination of the growth and on Mr. Page's state- 

 ment, given by Dr. Klein, as to the absorption-spectrum, 

 Avhich so far as it Avas observed (the colour not being very 

 intense) corresponds Avith that of Bacterio-purpurin — the 

 colouring matter of B. ruhescens. 



Variation in Colour. — The main fact on which I rely for 

 the identification of the various forms and aggregations of 

 plastids, assigned to Bacterium ruhescens as members of a 

 series or physiological species, is their agreement in colour. 



