352 



GRACE MEDES 



from normal sea- water to one of changed concentration; or sec- 

 ond, an influence directly injurious to growth during the earliest 

 stages of development in those solutions which later act most 

 favorably, such as a 10 or 15 per cent dilution. Solution aa is 

 one from which any element of shock must have been elimi- 

 nated. At the close of 24 hours it has a specific gravity of 

 1.0233, or 4.4 per cent greater than the control. If early inhibi- 

 tion during the first 24 hours were the results of unfavorable 

 conditions alone, we should expect the inhibition in growth in 

 each solution to increase gradually as the concentration becomes 

 greater, but instead we obtain the following results: 



Percentages of decrease in size compared with the control 



In the aa solution, the inhibition is sUght the first day, and 

 increases in intensity as the concentration gradually becomes 

 greater. In solution b +, the inhibition at the end of 24 hours 

 is only sHghtly less than that at the end of 48 hours. In c +, 

 the inhibition is greater at the close of 24 hours than at the 

 close of 48, after which it increases in intensity. The same is 

 true of solutions d + and e + to an even more marked degree, 

 and in the latter the recovery is not complete until the third 

 day. 



From these facts we may conclude that there is an early 

 and separate inhibition factor due solely to sudden changes 

 of medium and that subsequent inhibition or acceleration of 

 growth is a secondary factor which may operate independently. 

 In view of this, we may be justified in interpreting the early 

 inhibition produced in the solutions of high dilution, which 

 later cause acceleration in growth rate, as one due to the sud- 

 den change of physical conditions and not to a retarding effect 



