CYTOMORPHOSIS IN BACTERIA 149 



the medium, so few that they are not suitable for most types of ex- 

 periment. Every attempt to concentrate them, particularly to remove 

 them from their medium, immediately causes them to rapidly age, 

 and they are no longer physiologically young cells but mature cells. 

 For this reason I do not believe that very much experimental work 

 has so far been done with truly physiologically young bacteria. Some 

 way must be discovered for either working with small numbers of 

 cells in the medium in which they are growing, or else concentrating 

 them in some way that their properties are conserved, before much 

 can be accomplished in this direction. 



