SUPPLEMENT 73 



in question (WiLLE, 1902 ; MOLISCH, 1903). Other colourless sulphur-bacteria 

 have been discovered by OMELIANSKI (1905), HINZE (1903), and JEGUNOW 

 (comp. OMELIANSKI in LAFAR'S Mykologie, III. 214). JEGUNOW'S observations 

 on the movements of the forms he studied are of interest. When confined in 

 a tall narrow vessel, these plants congregate at a certain distance from the 

 upper surface of the fluid (as described above in the microscopic culture of 

 Beggiatoa) and proceed to make incursions from thence into the deeper regions 

 of the medium in what look like convection currents. Single cells migrate 

 downwards into the middle of the stream and at the same time load themselves 

 up with sulphur ; they then move back again to the outer edge of the stream, 

 upwards, and there oxidize the sulphur. The rapidity of the movement is con- 

 siderable ; they can traverse the whole distance back in five minutes. 



Associated with the colourless sulphur -bacteria there is a whole series of 

 so-called red sulphur-bacteria (Fig. 39, d, e), which physiological research has 

 already shown to exhibit important differences from Beggiatoa, although no 

 satisfactory conclusions have as yet been reached with regard to them. 



11. 43-5, for the question as to how ... in association read it is incom- 

 prehensible how they manage to obtain the necessary oxygen. According to 

 WINOGRADSKY (1888 b) they do so by always being in association 



224, 1. 5 P. 225, 1. 26, for It is to be hoped . . . nitric acids, read More 

 recently MOLISCH (1907) has reinvestigated this question. He was unable to 

 demonstrate any evolution of oxygen from purple Bacteria with the most varied 

 methods, so that one must still regard the existence of such a process as open 

 to the gravest doubt. It does not follow, however, that no CO 2 -decomposition 

 takes place. The oxygen produced might indeed we might say must be at 

 once used up in the oxidation of sulphuretted hydrogen. A normal assimilation 

 in these forms is all the more probable, since MOLISCH found that sunlight, 

 though not essential, was at least helpful. In another aspect MOLISCH disagrees 

 widely from WINOGRADSKY'S views. He finds that purple Bacteria can exist 

 without peptone, and he unites with these organisms also those forms which 

 contain the same colouring matter as the red sulphur-bacteria, though without 

 the sulphur. It would thus appear that he attributes no special vital signifi- 

 cance in these Bacteria to the sulphur. On the whole, we must admit that 

 further research on the subject is still urgently needed. 



A group of sulphur-bacteria with quite different peculiarities has been 

 discovered by NATHANSOHN (1902) in the Gulf of Naples, and BEIJERINCK (1903) 

 has shown that similar organisms occur in other seas, and are not wanting also 

 in fresh water. The forms observed by NATHANSOHN oxidize thiosulphate to 

 sulphuric acid and tetrathionic acid, according to the following formula : 



3Na 2 S 2 3 + 50 = 2Na 2 SO 4 + Na 2 S 4 O 6 



A separating out of sulphur occurs here also, but it does not take place 

 within the organism and is perhaps, so far as its origin is concerned, quite inde- 

 pendent of it. By the use of an agar-solution, to which has been added sea- 

 water and Na 2 S 2 O 3 , these organisms, like other Bacteria, may be cultivated and 

 isolated ; they do not exhibit that great sensitiveness to organic substances 

 that Beggiatoa does. The addition of organic bodies, such as sugar or urea, is of 

 no service to them, and does not enable them to 'do without thiosulphate ; hence 

 we must conclude that the oxidation of thiosulphate completely replaces the 

 respiration of organic bodies, and that it cannot be replaced by them. Thio- 

 bacillus thioparus, studied by BEIJERINCK, differs widely from NATHANSOHN'S bac- 

 terium, inasmuch as it can decompose not only thiosulphate but also sulphides 

 (calcium sulphide), sulphuretted hydrogen, and tetrathionate. The splitting off 

 of sulphur which always takes place must, according to BEIJERINCK, be always 



