140 Regulation of Size in Unicellular Organisms 



formation of cysts was induced in cultures poor in 

 metabolic products the cysts were smaller than those 

 induced in the ordinary way by ageing and starvation 

 of the cultures. Richness in metabolic products here 



8 16 24 



Age of culture in days 



32 



Figure 44. Effect of age of culture at 20° upon Colpidium colpoda. A, 

 Relative body volume of one individual; B, Relative concentration of the 

 Colpidia in the culture fluid; C, Total substance of all the Colpidia present, 

 i.e. A multiplied by B. (Data of Vieweger, '25, expt. Ilia). 



gave rise to increased sizes, representing a mean body 

 "old" culture fluid has by this means been found to be 

 detrimental to reproduction. 



Belar ('24) demonstrated the effect of products of 

 metabolism in the heliozoan Actinophrys. When the 

 volume 49 percent larger. Diversities in hydrogen ion 



