384 M3'-xomycetes. 



The author has further studied on the swarm-spores of Aetha- 

 lium septicum the "ring coUection" formed at the end of the capil- 

 lary tube, the "column collection" within the tube itself and also 

 the action of the concentrated Solutions of the chemicals upon the 

 movement of the swarm-spores, and thus the relation between each 

 acid or acid Solution and the Chemotaxis was made out. 



The size and the tickness of the ring collection and the degree 

 of the distinctness of its margin are different according to the nature 

 of the acids used, though the capillary tube is fiUed always with 

 1 — mol. acids. When strong acids, as for example mineral ones, 

 are used the ring has the longer diameter, but it is thin and sharply 

 limited. The production of the clear repulsion Space within the ring 

 of such acids depends upon the supraoptimal concentration of 

 H-ions and the outermost portion of this space contains ca -^ gr. 

 H-ions per litre. 



In many organic acids, however , the repulsion space is not 

 formed on account of the supraoptimal concentration of H-ions, but 

 is formed generally by the repulsive action of free molecules, or in 

 other words, when the swarm-spores attracted hy H-ions attain the 

 Zone with the larger quantity of molecules, the}^ are prevented to 

 advance towards the end of the tube and thus form the ring collec- 

 tion. So in this case the size of the repulsion space, the thickness 

 of the ring, the degree of the distinctness of its margin depend 

 exclusively upon the degree of the dissocation. Malic, succinic and 

 tartaric acids of -^-J-^ mol. concentration repel the swarm-spores on 

 account of their undissociated molecules; that this action is not due 

 to their osmotic property (i. e. withdrawel of water) is clear from the 

 behaviour of chemotactically indifferent substances as potassium 

 nitrate or sodium acetate, which cannot prevent the advance of 

 the swarm-spores towards the zone of higher concentration, unless 

 they are at least in the concentration of ^ mol. 



The swarm-spores react phototactically, whether attracted or 

 repelled. The author has traced their motion in several cases and 

 figured their motor path. 



In Order to determine the minimum concentration of various 

 reagents , which produces the chemical Stimulus ("Schwellenwert") 

 the author does not use the usual capillary method of Pfeffer, because 

 the latter method gives in this case too inaccurate results. Many 

 acids do not attract the swarms-spores towards the end of the tube, 

 unless they are so concentrated as to produce the toxic action; 

 for example HCl must be in the concentration of ^^^ mol. For this 

 purpose he has adopted the following method, which consists in 

 introducing the spores of the culture medium in a tube closed at 

 one end and inserting the open end into the Solutions of various 

 concentrations. He has thus determined the degree of concentration 

 which produces the first reversal of the motion of the swarm-spores 

 and found the „Schwellenwert" for CHI tuwct "CdoX. and for 

 H2SO4 -^-^U-^ mol. 



Stange has found that many acids are chemotactically inactive 

 towards the swarm-spores of Myxornycetes. The author thinks that 

 this is due to the fact that S. has used too narrow tubes, for even 

 in comparatively higher concentration acids do not act at all, unless 

 the tube is at least 0,1 mm. in diameter. 



The acidic substances have the power of promoting the germi- 

 nation of the spores and the fact that the spores of the Myxorny- 

 cetes growing upon decomposing vegetable matter are promoted in 



