Nov.. iGiti.] r. KUWADA.—SOME PEC ULFAJIITIES OBSERVED. 353 



from time to time (or the duration of a few seconds. I>oth ex- 

 periments were repeated several times with the same results. 

 It shows therefore that the peeuliai- i)henomenon mentioned 

 above is simply related to the convection current of water. It 

 is noted here that the phenomenon is exhibited by the swarm- 

 spores only, and never by the non-motile form which is always 

 found near the surface of water. An attempt to induce the same 

 phenomenon purel}^ physicall}^ by cooling or warming a part 

 of water containing some green powder failed. 



In the above mentioned experiments the columns appeared 

 onh^ at the one side of the flask, and not at the inner parts of 

 it. Naturall}' it appears, however, simultaneously at all the 

 positions either peripheral or central of the surface of water. 

 Such a difference is due perhaps to the condition that in the 

 former case the main difference of temperature was between 

 both sides of flask, while in the latter it is rather between the 

 surface and bottom. 



As metioned above, the green columns make their appear- 

 ance in the light as well as in the dark, and hence there is no 

 relation to light. But one morning, to my astonishment, a 

 peculiar sight burst on the view, that the green columns were 

 regularly arranged in lines toward the direction of ray of light 

 (Fig. 4). To make clear whether it depends on the light stimulus 

 or not, I turned the vessel through 90° so as to make the 

 direction of the lines perpendicular to that of the ray of light. 

 The arrangement soon disappeared and after a little time a 

 new arrangement toward the direction of ray quite in the same 

 manner as before was established. Fig. 4 is ^i photograph 

 taken after this rearrangement of swarmspores. In Oltmanns' 

 observations the length of the columns was longer in the darker 

 region than in the lighter. 



Though I could not thoroughly analyze the whole pheno- 

 mena, it is heighly conceivable that it would be nothing but an 

 outward expression of the negative rheotactic nature of the 

 organism. In the last mentioned case not only the rheotactic 

 activity but also the phototactic activity would have played a 

 role. That it was observed onh^ once w^ould probably rest on 



