350 I'HE BOTANE^AL MAGAZINE. [Vol. xxx. No. 359. 



way is only transitor3\ Mast'' records in his book, that he failed 

 in Chlamydomonas to get a positive result by adding QO.,. But 

 he means, it seems to me, that the reaction did not occur im- 

 mediatclj^ after the operation as is the case with other organisms 

 with which he succeeded in turning the sense of their phototaxis. 



One may object in saying that rather the mechanical agita- 

 tion produced b}^ bubbling the gas would be the cause than 

 the change of the chemical condition of the medium. 1 have 

 not an3' positive evidence to serve as a criterion, because I 

 failed unfortunately to make a control experiment owing to the 

 want of sufficient materials. Nevertheless we can maintain that 

 the sense of reaction of the present organism ma\' be subjected 

 to change by certain external agents. The influence of tempera- 

 ture upon Chlamydomonas was studied by Mast.-^ 



The difference of behaviors caused by chemicals is also to 

 be recognized in the cases of culture medium containing potas- 

 sium nitrate (p. 347) and the following case where potassium 

 nitrate is replaced by ammonium chloride. 



The particular observations to be reported here is, however, 

 what were observed in the culture with ammonium chloride as 

 the source of nitrogen. In this culture the organism reproduced 

 mostly in non-motile form and was found near the surface 

 of w^ater in contrast to the case with the first culture, in which 

 onl}' swarmspores were produced and they used to swim at the 

 bottom of the flask showing a clear phototactic activity'. As 

 the culture became old the swarmspores also appeared in this 

 culture, but their behavior to light differed from those in the 

 first, being rather indifferent to light stimulus. Thc}^ were 

 swimming near the surface of water making a thick green 

 layer thereat, and never found at the bottom in the least. But 

 when the number of swarmspores became considerabh'' increased, 

 only a part of them sank to the bottom and showed a 

 sign of the reaction to light. In this stage of culture a jicculiar 

 phenomenon came across our view which was the main ]")oint 

 of the present report. 



1) Mast, S. O., Light and the Behavior of Organisms. 1911. 

 2j Mast, S. ()., I.e. I'Jll. 



