EFFECT OF EXCRETION PRODUCTS OF PARAMAECIUM 581 

 CONCLUSIONS 



In this paper are presented the initial experiments of a series 

 which is planned to elucidate, if possible, some of the complex 

 factors at work in a 'hay infusion,' for example, such as those 

 which determine the interdependence of the organisms, their 

 sequence, time of appearance and disappearance, etc. The data 

 outlined were derived from the study of the following points: 



(1) The effect of different volumes of culture medium on the rate 

 of reproduction of Paramaecium; (2), The effect of changing the 

 culture medium daily and on alternate days on the rate of repro- 

 duction of Paramaecium; and (3), The effect of culture medium, in 

 which many paramaecia have been living, on the rate of reproduc- 

 tion of Paramaecium. It is believed that the results obtained 

 justify the following conclusions: 



1. The rate of reproduction of Paramaecium aurelia and Para- 

 maecium caudatum is influenced by the volume of the culture 

 medium, within the limits tested, and the greater the volume the 

 more rapid is the rate of division. 



2. Paramaecia excrete substances which are toxic to themselves 

 when present in their environment, and these substances are 

 more effective when the organisms are confined in limited vol- 

 umes of culture fluid, 



3. The excretion products of paramaecia play an appreciable 

 part in determining the period of maximum numbers, rate of 

 decline, etc., of this animal in 'hay infusions.' 



