POWER OF SELECTION. 47 



found that while lithium chloride caused abnormal cell forms 

 in Bacillus megatherium, B. typlti abdominalis, Vibrio cholerce 

 asiaticce, and Bacterium coli commune, it had no apparent influ- 

 ence on the cells of Bacillus subtilis, B. anthracis, and other 

 microbes. 



The quantitative selective power referred to above must not be 

 understood in the sense that the organisms inhabiting the nutrient 

 medium always have the same composition, irrespective of the 

 relative proportions of its nutrient constituents. E. CRAMER (I.) 

 studied this matter exhaustively in relation to several patho- 

 genic bacteria and Micrococcus prodigiosus, and arrived at the 

 conclusion that a typical composition of any species is out of the 

 question. According to the kind of medium, the temperature and 

 age of the culture, and other conditions, it may happen that one 

 crop will contain twice as much of a particular constituent as 

 another crop. Thus, for example, the amount of dry matter 

 varied from 15.9 to 26.0 per cent., and of ash from 1.60 to 3.21 

 per cent. 



