LARVAE OP ARBACIA PUNCTULATA 



349 



The primary inhibiting effect of the various degrees of dilu- 

 tion may be seen by a comparison of the points of their growth- 

 curves (Plot 5) at the 24 hour period. These points fall from 

 38.10, the size of the control, through 37.14, the average of 

 culture aa, started in normal sea-water and allowed to evapo- 

 rate for 24 hours, and terminate with 17.34 {g), started in 30 



Plot 5 



Plot 6 



per cent dilution but now evaporated to 95.7 per cent of its 

 original volume. 



In the solutions of greater concentration than that of normal 

 sea-water each culture showed a corresponding decrease in 

 size, until in e + the skeletons were represented merely by 

 minute tri-radiate spicules of very nearly the same size as 



