RATE OF GROWTH OF BACTERIA 45 



Penfold has suggested another theory that deserves mention, 

 namely that "the inoculum consists of organisms having individually 

 different powers of growth, and that during the lag the selection 

 of a quick growing strain occurs in response to some selecting agent 

 in the peptone". This explains the gradual acceleration of growth 

 in the true lag phase. It will be seen from later chapters that such 

 individual variations in power of growth occur, and that a selection 

 of a rapidly growing strain may take place. 



