( 22 ) 



take in a now provision of oxygen. Outside the accumulation, ileal' 

 the edge of the cover-glass, where tlie pression of oxygen increases, 

 the number of bacteria diminishes quickly, together with the mobility 

 of the remaining ones. At the edge itself all is in complete rest, 

 and no motion sets in when the surrounding- is freed from oxygen. 

 Still 1 have no reason to consider the resting individuals as dead; 

 I even think they function as an „oxygen filtrum", thus protecting 

 the more inwardly swarming. 



If some grains of fibrine are introduced into preparations of 

 which the figures of respiration are being studied, and if placed at 

 c a. 25° C. in a „humid room", a considerable increase of bacteria 

 may readily occur. Watching the process micros- and macroscopically, 

 we find the growth almost exclusively limited to the accumulation 

 parallel to the edge, which accumulation grows more and more dense by 

 the increase of the spores, whilst the central part continues as clear 

 as at first. Consequently, it may be taken for granted that 7^.. st^j//chs 

 requires oxygen for its growth, as well as for its mobility. 



On this occasion I wish to correct a mistake in my description 

 of Spirillum desulfuricans. I there stated erroneously ^) that Spi- 

 rillum ienue, which is typical for microacrophily as to mobility, 

 is also microacrophilous with regard to growth, so that, when sown 

 in a fit culture mass, it shows its maximum growth, not at the 

 surface, but at a certain distance below it. 



This has proved to repose on „trophotropy", signifying that growth 

 is more favored by the influence of the food than by the oxygen. 

 It occurs only when a bad culture ground is taken for the experi- 

 ment, and it is by the acrophily of the growing spirilli that it must 

 be explained. For the intense growth will cause at the surface a 

 rapid exhaustion, so that, if no abundance of food is pr^'sent, and 

 if the food can only come up slowly from the depth by the process 

 of diffusion to the place of consumption, then, not the surface itself, 

 but a deeper layer will, under the joined action of oxygen and 

 food, be most favorably situated for growth and increase. Thus in 

 fact, Spirillum tenue is acrophilous as to growth and mieroaërophilous 

 as to mobility. 



Beside to this peculiar form of „tropliotropy" in the growlh, one 

 has to pay attention, when studying the figures of respiration, to a 

 phenomenon of almost the same nature with respect to the mobility, 

 and which may be called „trophotaxis". It consists in the accumu- 



1) Archives Nt'erkiulnises, T. 29, pag. 272. 



