MECHANISM OF COMPETITION IN YEAST CELLS 69 



cells adapt themselves to the medium. This is because we used for 

 inoculation fresh yeast cells developed in a medium of an identical 

 composition with those used in the experiment. This circumstance 

 has been pointed out by Richards ('32). 



(2) An investigation of the shape of the curve which represents 

 the accumulation of the yeast volume in the population of yeast cells 

 does not enable us to judge what factors control the growth of the 

 population and limit the accumulation of the biomass. The fact 

 that the growth curve is S-shaped and resembles the well-known auto- 

 catalytic curve does not prove at all that the phenomenon we are 



Fig. 9. Growth in volume of the yeast, Saccharomyces cerevisiae. From 

 Gause ('32a). 



studying has anything in common with autocatalysis. The question 

 of the basic nature of the yeast growth in a limited microcosm can be 

 elucidated only by means of specially arranged experiments. Such 

 experiments were recently carried out by Richards ('28a) and con- 

 firmed by Klem ('33). 



We have already mentioned that the process of multiplication of 

 organisms is potentially unlimited. It follows the law of geometric 

 increase, and limitations are here introduced only by the external 

 forces. In the case of yeast this circumstance was noted by Slator 

 ('13), and recently Richards carefully verified it in the following 

 manner. A control culture after the inoculation of yeast was left 



