Nov. 1907.] 



KUSANO. -PIIOB 0- CHE MOT AXIS OF MYXOMYCETES. 149 



The least amount of acid-molecules or H-ions necessary to 

 exercise a just observable repellent action may be approximate- 

 ly determined as follows. Fresh material of swarm-spores is 

 transferred into the vessel with various degrees of concentration 

 of acids and then it is observed at what degree the spores are 

 so injured, within 40-60 minutes, as to assume round forms 

 and to become incapable of moving actively. The critical value 

 of each acid thus obtained is as follows : 



Hydrochloric acid 1/600 mol. 



Nitric acid 1/600 mol. 



Sulphuric acid 1/700-1/800 mol. 



Oxalic acid 1/600 mol. 



Acetic acid 1/600-1/700 mol. 



Malic acid 1/500 mol. 



Tartaric acid 1/500 mol or above. 



From these we may learn that the concentrations of acids 

 which exist at the outermost of the repulsion space or, in other 

 words, at the inner margin of the ring, will be approximately 

 similar to the value given in this table. At a higher concentra- 

 tion than 1/600 mol the repellent action of hydrochloric acid 

 is due to H-ions while that of acetic acid is due to its molecules. 

 The table points out also that the repulsive space is greatest 

 with sulphuric acid and smallest with malic and tartaric acids, 

 which accords with the facts obtained by the experiments 

 already given. 



The responsiveness of the swarm-spores to acid-molecules 

 seems to be more feeble than to H-ions, for the spores at the 

 inner margin of the ring, where the acid-molecules predominate 

 over the H-ions, sometimes can not escape the injurious action 

 of the molecules, as the attractive action of H-ions here 

 overpowers the repulsive action of molecules. 1 ) 



The injurious action of acid-molecules here concerned is 



J ) Acetic acid dissociates at J/512 mol only 9.14^ and at 1/1024 mol, 12.66^. 

 The co-existing ac'd-molecules are therefore much more than the H-ions. 



