148 Regulation of Size in Unicellular Organisms 



ure 50 shows that, after acclimatization to the salt 

 solution was complete, the mean bulks were just as 

 large in concentrations up to M/20 as in the control 

 medium. This is evidence, for one species of ciliates, 

 that changes of total concentration are not significant 



8 16 £4 32 40 



Time In solution in minutes 



Figure 49. Progression of body length and body volume (calculated as 

 / X b 2 ) in a culture of Paramecium which was transferred, at zero time, into 

 a 0.10 M solution of sodium chloride made up in hay infusion. At each 

 of the times indicated 50 individuals were fixed and measured. (Data of 

 Estabrook, '10). 



factors in the influence exerted by ageing of medium. 

 But in concentrations above M/20 sodium chloride, the 

 osmotic pressures of the medium have marked effects 

 upon body size; evidently reversible dehydrations or 

 swellings are produced. 



