432 



GEO. T. HARGITT AND WALTER W. FRAY 



cent, 0.1 per cent, 0.2 per cent, respectively. At the same 

 time a 0.025 per cent solution of Liebig's extract of beef in tap- 

 water was made. 



The sister cells obtained by several divisions of a single Para- 

 mecium were distributed between the various fluids and grown 

 for some time, being changed to fresh solutions daily. The 

 results for growth during two weeks are shown in tables 1 and 2. 



Tables 1 and 2 show that deaths were frequent in the 0.2 per 

 cent hay infusion, and with both P. aurelia and P. caudatum the 

 results showed the superiority of the 0.1 per cent hay infusion 

 and the 0.025 per cent beef extract solution. From this time 

 on the 0.1 per cent hay infusion was used as the culture fluid 

 for all work. Occasionally the 0.025 per cent beef extract was 

 used and its use will be indicated each time. The hay infusion 

 was used rather than the beef extract solution, in order to have 

 the solutions of the same sort as an ordinary infusion. The 

 objection might be raised that since Woodruff, and Woodruff 



TABLE 1 



GrowtJi, of Paramecium aurelia in mixed cultures of bacteria, in media of different 

 concentrations. Figures represent number of divisions. H. I., hay infusion; 

 B.B., beef extract; ^ dead replaced from 0.1 per cent hay infusion 



Paramecium aurelia I 



0.05 per cent H. I.. 



0.1 per cent H. I 



0.2 per centH. I... 

 0.025 per cent B. B. 

 Filtered infusion. . . 



2.5 



28 



29 



30 



TOTAL 

 DIVI- 

 SIONS 



21 

 23 

 16 

 20 

 18 



AVER- 

 AGE DI- 

 VISIONS 

 PERDAY 



1.615 



1.769 

 1.231 

 1.538 

 1.384 



Paramecium aurelia II 



0.05 per cent H. I. 

 0.1 per cent H. I. . 

 0.2per cent H. I... 

 0.025 per cent B.B. 

 Filtered infusion. . 



1.538 

 1.615 

 1.153 

 1.692 

 1.538 



