270 F. JEFFREY BELL. 



with a most remarkable phenomenon ; from which it may be 

 very justly concluded, without fear of appearing hasty in 

 drawing conclusions, that one form of activity in the circle 

 of vital processes which certain organisms exhibit, is the 

 production of free sulphuretted hydrogen, under suitable 

 conditions. 1 



16. The curious highly refracting granules noticed so 

 often already in the red-coloured organisms are similar to 

 those which have been observed in Beggiatoa ; they are, as 

 Cohn shows, particles of sulphur. 



By heating Beggiatoa- fibres on a slide the granules are 

 caused to melt and form a large yellow drop, Avhich gives 

 oflf the smell of sulphurous acid ; this experiment leaves no 

 doubt as to their being sulphur ; with polarised light they 

 are doubly refractive, but their small size and high refractive 

 index make it impossible for us to see their crystalline form. 

 Similar experiments have succeeded with Clathrocystis, 

 Monas, and Ophidomonas. 



The question asked just above is now fully answered in 

 favour of the living organisms. 



17. The suggestion that Bacterio-purpurin is due to the 

 formation of sulphur commends itself to Cohn, although he 

 is unable to prove the truth of it, as yet. Mr. Lankester has 

 pointed out that this colouring matter differs from that 

 found by Schroter in Micrococcus prodigiosus , and Cohn 

 points out that both differ, in the absence of chlorophyll, 

 from the colouring matter of Palmella cruenta and other 

 plants, such as the Phycochromacece. 



18. Blood-coloured milk was observed to owe its appear- 

 ance to the colouring matter of M. prodigiosus, which Cohn, 

 by the way, finds to be soluble in alcohol and other, unlike 

 Bacterio-purpurin, as well as in the fat-globules (Butter- 

 tropfchen) of milk. An interesting use of the microspec- 

 troscope is also noted; Cohn recognised the colouring 

 matter of M. prodigiosus in a capillary vessel containing the 

 red milk, where he was unable to recognise by the micro- 

 scope the forms of the organism which produced it. 



19. Our author remains true to his original position, that 

 the Bacteria may be arranged in two series ; one containing 

 Micrococcus and Bacterium, which run parallel to the Chroococ- 

 cacea, and pass through a resting or zoogloea stage, while the 

 other contains Bacillus, Vibrio, and Spirillum, which run 

 parallel to the OscillaricB, and pass through the Leptothrix, as 

 their resting stage; and this, although many of the Oscil- 

 lariee become surrounded by gelatinous membrane, that is, 



^ The Euglenae also exist and increase in such waters. 



