LARVAE OF ARBACIA PUNCTULATA 



347 



less modification if subjected gradually to the changed conditions, 

 and of determining what regulations, if any, would occur in the 

 process of adjustment. 



Solutions similar to those used in the preceding experiment 

 were prepared and were let stand in the open air with a con- 

 trol kept closely covered to prevent evaporation. A second 

 control was allowed to evaporate along with the other experi- 

 mental solutions. The temperature of the sea-water at the 

 beginning of the experiment was 17.25°C. The volume and 

 specific gravity of each solution were taken every day, and at 

 the close of the experiment the estimated specific gravity was 

 checked against the determined. 



Five dishes of each of the various solutions were set out 

 together at the beginning of the experiment, and all allowed to 

 evaporate. Each day one of these was utilized to supply the 

 corresponding culture with fresh medium. 



