Ii8 



Scientific Proceedings (34). 



varied environment. I wish now to bring the results up to date 

 (May 26, 1909). 



A culture of Paramecium aiirelia {caudatiwi) was started on 

 May I, 1907, with a "wild" individual isolated from a laboratory 

 aquarium, and during the twenty-five months which have elapsed 

 since that time it has been under daily observation. Infusions of 

 hay and grass together with any material that may be found in the 

 normal habitat of Paramecium have been employed as a culture 

 medium. The possibility of contamination by cysts or " wild " 

 Paramecia has been eliminated by boiling the infusion. Daily iso- 

 lation of an individual from each of the various lines of the culture 

 has enabled an accurate record of the division rate to be kept and 

 has precluded the possibility of endogamous conjugation. 



So far the culture has attained the 1,185th generation. The 

 average rate of division for the entire period is over one and a half 

 divisions per day. The average rate has not fallen during any 

 ten-day periods as low as one division in two days, while during 

 several ten-day periods it has averaged over two and a half divisions 

 per day. Marked physiological depression has not been indicated 

 by the rate of division and consequently special stimuli have not 

 been employed to " rejuvenate " the organisms. 



The results thus far obtained certainly show that the life cycle 

 of Paramecium when subjected to a varied environment may be of 

 very great duration, and, I believe, strongly suggest that the life 

 history may be of unlimited duration. 



63 (401) 



Immunity to various species of trypanosomes induced in 

 mice by the cure of experimental infections. 



By B. T. TERRY. 



\From the Rockefeller Institute for Medical Research. '\ 



When properly treated a temporary immunity was secured 

 against the organisms of surra of India, surra of Mauritius, caderas, 

 dourine and nagana. The immunity was specific in the sense that 

 it was active against the species cured but not against any other. 

 The immunity varied with the virus, the medicament, the time at 

 which the immunity tests were begun, the number of the tests, the 



