354 THE BOTANICAL MAGAZINE. [Voi. xxx. No. 359. 



the unknown condition of environment. It has been studied by 

 various investigators that the sensibility to stimuli nnd the 

 condition of environment have intimate relations to each other. 



Such rheotactic motion of organisms due to the vertical 

 current of water ma\' explain some of the phenomena relating 

 the hourK' or daily change of vertical distribution of plankton 

 organisms. 



In passing, a short note on the chemotaetic activity of the 

 present organism may be added. It is one of good materials 

 for demonstrating the phenomenon owing to its green colour 

 which makes the observation easier than do the colourless or- 

 ganisms as bacteria, spermatozoids, &c. It responds positively 

 to both organic and inorganic acids, if the concentration is 

 adecjuate. The chemical agents used as chemotaetic stimuli 

 were the following : — 113'drochloric acid, nitric acid, sulphuric 

 acid, chromic acid, osmic acid, picric acid, oxalic acid, succinic 

 acid, malic acid, maleinic acid, fumaric acid, and lactic acid. It 

 shows also the strog chemotaetic activity to those agents with 

 acidic propcrt}^ as flesh extract, " Ajinomoto " or natrium 

 glutaminate, etc. It was shown that the chemotaetic activity 

 induced by " Ajinomoto " was due merely to the acidic property 

 of its impurity in having been examined that the responsibility 

 decreased to about one tenth of that of ordinar}' one when 

 chemically purer, less acidic sam])le was used. The neutral 

 chemicals such as ammonium chloride, ^^ potassium nitrate,'-' 

 calcium nitrate, etc., gave no influence upon the organism that 

 is to say, the organism was indifferent to those chemicals. 

 Pepton was on the other hand attractive nearly so strong as 

 flesh-extract, though the acidity, if ])resent, was not so remark- 

 able as to be detected by means of litmus-paper. It has been 

 examined also by Pfeffer"' that jjcpton is attractive in the 

 case of Chlamydomonas pulvisculus. 



1) 'Jlie medium, in wliicli tlie organism used for tliis experiment was cultured 

 contained P/^^ KNO3 as the source of nitrogen, and not JsII^Cl. 



2) The organism placed at this disposal wa.s from the same source of culture 

 as in 1). The reaction was not induced cvi n witli 10% solution of potassium nitrate. 



3) Uutcrs. hot. Inst. Tubingen. II. IbSS. 



