128 W. J. ROBBINS. 



Kusano (3) has described similar reactions of the swarmspores of 

 Myxomycetes to acids. He attributes them to chemotaxy. 

 An examination of individual spermatozoids, however, showed 

 no change in the direction of their movements passing the mouth 

 of the tube, the effects could by no means always be obtained, 

 and much the same result was observed in one case with HC1. 

 I believe that the results could be interpreted as a toxic phenom- 

 enon as explained below. 



In the case of the. molecular concentration, the diffusing acid 

 is sufficiently strong to kill or paralyze the spermatozoids through- 

 out the whole mount. With acid of o.i Mol concentration the 

 diffusing zone of the acid which is toxic is not so wide as in the 

 case of acid of the molecular concentration and only those sper- 

 matozoids are rendered non-motile which pass comparatively 

 close to the mouth of the tube; hence the collection observed 

 after a time around the mouth of the tube. At the concentration 

 of o.oi Mol the diffusing acid is not toxic, and only those sper- 

 matozoids are rendered non-motile which pass comparatively 

 close to the mouth of the tube; hence the collection observed 

 after a time around the mouth of the tube. At the concentration 

 of o.oi Mol the diffusing acid is not toxic, and only those sper- 

 matozoids which enter the tube, as some must from several 

 hundred of individuals in a mount, are paralyzed and remain 

 there. Acid of o.ooi Mol concentration is below the toxic con- 

 centration and we have no effect. We do not find the effects 

 noted above in every mount where the acids are used because 

 there may be an accumulation of all active spermatozoids due to 

 negative phototaxy on the side away from the source of light, 

 in which case they do not meet the acid diffusing from the tube; 

 or there may be too few individuals in the mount to show distinct 

 collection; or they may not be actively motile due to the high 

 temperature or old material. 



If the results noted are due to a toxic effect of the acids on the 

 spermatozoids, it would be expected that other substances, such 

 as potassium hydroxide and ethyl alcohol should also produce 

 the reaction. While no response to those substances was noticed, 

 this may have been due to poor material or to too high a tempera- 

 ture at the time of the experiment. In either case the spermato- 



