Botany. — ''On the influence of electrolytes on the motility of 

 Chlamydomonas variabilis Dangeard" . By C. Spruit P.Pzn. 

 (Oomiiinnicated by Prof. Went). 



(Communicated in the meeting of November HU, 1918). 



The reactions of unieellular motile organisms to external stimuli 

 are not always equally prompt. We speak of "condition", probably 

 due to one or more of these incalculable factors which make experi- 

 ments with living organisms so troublesome. 



Ill the case of Cldamydomonas variabilis Danyeard I have found 

 that the case of response of this unicellular, motile green Alga to 

 light, gravity or chemotactic stimuli depends not only on the nature 

 of the dissohed substance, but also on its concentration. By systematic 

 investigation of the motility of the Alga in solutions of a few sails, 

 an attempt has been made to obtain some idea of the manner in 

 which electrolytes influence this phenomenon. Although it wotdd 

 have been desirable to investigate the influence of numerous electro- 

 lytes, it has nevertheless become clear from the data collected hitherto, 

 that the action of electrolytes on the motility of Chlamydomonas 

 agrees in many respects with their action on the solution and preci- 

 pitation of colloids. 



A culture method, indicated by Jacobsen ^), was employed in order 

 to make large quantities of Chlamydomonas species available. 



After cultures had been obtained continuousl} for some months 

 by inoculation, the experiments were undertaken. Part of each culture 

 employed was fixed with formalin. Determination showed that the 

 cultures always contained almost exclusively individuals of (Jhlamy- 

 domonas variabilis Danyeard. 



Under favourable conditions this species is sensitive to light, to 

 gravity and to some chemotactic stimuli. Under certain conditions 

 the Alga reacts also to contact, by attaching itself to solid objects. 

 In the experiments Chlamydomonas generally reacts negatively to 

 light, sometimes a positive reaction is observed. The latter was more 

 frequently the case if the alga remained in the culture fluid. 



Under the influence of gravity an obvious and rapid positive 



^) H. G. Jacobsen. Zeitschr. f. Bot. Bd. II 1910. 



