I9I2] Lorande Loss Woodruff 409 



excretion products to be one of the most important. The interde- 

 pendence of the organisms of a hay infusion is so complex that, 

 taken as a whole, it is almost beyond the possibility of analysis, and 

 therefore the logical method of approach to the subject is to study 

 the interactions of isolated organisms and small groups of organ- 

 isms on themselves and on each other. 



Accordingly there have been made the initial experiments of a 

 series which is planned to elucidate, if possible, some of the com- 

 plex factors at work in a hay infusion; for example, those which 

 determine the interdependence of the organisms, their sequence, 

 time of appearance, disappearance, etc.^* The data outlined were 

 derived from the study of the effect of different volumes of culture 

 medium on the rate of reproduction of Paramcücium; the effect of 

 changing the culture medium at twenty-four and forty-eight hour 

 intervals on the rate of reproduction; and the effect of culture 

 medium, in which many paramsecia have been living, on the rate of 

 reproduction. 



In the series of experiments which were made to determine the 

 effect of different volumes of culture medium, the volumes selected 

 were two, five, twenty and forty drops. In brief, the daily rate of 

 the organisms in two, five, twenty, and forty drops of culture medium 

 changed every twenty-four hours showed that, for example, those 

 in five drops divided 2.4 per cent. more rapidly than those in two 

 drops, those in twenty drops divided 6.4 per cent. more rapidly than 

 those in two drops, and those in forty drops divided 7.4 per cent. 

 more rapidly than those in two drops. It is believed that the experi- 

 ments were sufficiently comprehensive to establish clearly the fact 

 that the rate of reproduction of paramsecia is influenced by the 

 volume of the culture medium (within the limits tested in the ex- 

 periments), and that the greater the volume the more rapid is the 

 rate of division. 



It being clear that in an increased volume of culture medium 

 there is increased division rate, the next point of importance was 

 to determine to what factor or factors this is due. It is evident 

 that it may be the result of variations in temperature, pressure, 



" Woodruff : Effect of excretion products of Paramcecium on its rate of 

 reproduction. Journ. Exper. Zoology, vol. lo, no. 4, 191 1. 



