350 GRACE MEDES 



those in the corresponding culture of Experiment 2. Mean- 

 while, however, the solution had become concentrated by evapo- 

 ration to a specific gravity of 1.02797, a concentration slightly 

 greater than that of solution / + , Experiment 2, specific grav- 

 ity 1.02788, in which development had not passed beyond the 

 blastula stage. 



At the end of 24 hours, all the cultures in the experiment 

 were in the same order, as regards size, as those in Experiment 

 2 had been at the same age, and showed about the same inhi- 

 bition of growth, although they were now in sea-water of 

 approximately 4.3 per cent greater concentration. 



The specimens in aa averaged slightly less than those in a, 

 and, since these two cultures were started in normal sea-water, 

 this decreased rate of growth cannot be ascribed to any pri- 

 mary inhibition due to sudden changes of osmotic pressure, 

 but must have been due to the gradually increasing concen- 

 tration. This effect was still more evident on the following 

 days. Inhibition became more pronounced as the solution 

 became more concentrated, until, at the end of 72 hours, a 

 specific gravity of 1.02790 was attained. This was sHghtly in 

 excess of that of solution h, Experiment 2, in which the eggs 

 failed to develop beyond late cleavage. 



In the cultures with diluted sea- water the early effects were 

 similar to those in the corresponding solution of Experiment 

 2; but, as concentration gradually took pUce, secondary effects 

 were produced. On the one hand, as those solutions of mod- 

 erate dilution became evaporated to a density greater than 

 that which Experiment 2 showed to be the optimum for growth, 

 the effects specific to concentration replaced those peculiar 

 to dilution; and the secondary characteristics were more evi- 

 dent the earlier the time of their appearance. On the other 

 hand, in those cultures which were initially diluted more highly 

 than was advantageous for growth, such as e, / and g, there 

 was produced an early inhibition of growth. But as the medium 

 became less injurious, secondary readjustment occurred and 

 growth became more rapid as the concentration approached the 

 ideal range. 



