28 



A. YASUDA. 



increased in size as well as in number while their bodies became much 

 thicker, with outlines presenting a more or less rounded appearance. 



Of the five external media I used the sugar-solutions proved to be 

 the best adapted to the organisms, the highest degree of adaptation 

 being possessed by milk-sugar, then followed cane-sugar and next grape- 

 sugar. Glycerine was found to be better adapted than common salt. 



It is evident that the action of the above substances is not due to 

 the degree of their concentration but to their chemical nature ; for the 

 solutions which were in isotonic concentration did not have the same 

 effect upon the organisms. Thus, in the cultures of Colpidium colpoda, 

 for example, 8% cane-sugar, which is isotonic with HA% milk-sugar, 

 4.2% grape-sugar, 2.2% glycerine and 0.9% common salt, formed the 

 highest limit, together with 10% milk-sugar, 7% grape-sugar, 5% 

 glycerine and \% common salt, so that the limits in the latter case were 

 generally found to be far higher than those in the former, except with 

 common salt where, on the contrary, the adaptation of the organism 

 was much lower. A similar observation was made by Stange,^ who 

 found that isotonic solutions caused various growth-rates in the bodies 

 of plants. 



Conclusions : — > 



(1) Isotonic solutions of the chemical compounds in question do not 

 produce corresponding effects upon the bodies of infusoria. The action 

 depends more upon the chemical nature of each substance than upon 

 its concentration. 



(2) In solutions of higher concentration a contraction of the bodies 

 takes place, which disappears after some hours, when the organisms 

 begin to accommodate themselves to the new media. 



(3) Higher concentration of the medium retards the multiplication 

 of the organisms. 



(4) As the concentration of the medium increases, the movement of 

 the organisms is retarded. 



1) B. Stange, loc. cit. Nr. 22, p. :iGi. 



