ACTIVATION OF UNFERTILIZED SATRFISH EGGS. 



277 



the results of four series of experiments at this temperature. 

 The August eggs were less favorable than the June eggs. 



Two similar series at 35° and one at 36° were carried out in 

 June at a time when starfish eggs were unusually favorable. The 

 results were similar to those at 33° and 34° except that the physio- 

 logically equivalent exposures were shorter. At 35° an exposure 

 of 30 seconds induces membrane-formation in many but not in 

 all eggs, and one of 45 seconds in practically all. At 36° 15 

 seconds is sufficient to form membranes in about half the eggs 

 and 30 seconds in all. Longer exposures eventually interfere 

 with membrane-formation ; thus after 6 to 8 minutes at 36° mem- 

 branes failed to form or were imperfect in 40 to 50 per cent, of 

 eggs. Table VIII. gives the proportions of eggs forming swim- 

 ming larvse in these experiments. The transfers from warm to 

 normal sea-water were made at first at intervals of fifteen seconds. 



Table VIII. 



35° and 36°. 



The rapid decrease in the optimum exposures as the tempera- 

 ture rises is to be noted; the optima are respectively i}^ to 2 

 minutes at 35°, and i to i34 minutes at 36°. 



Variation with Temperature in the Rate of the Process 

 Underlying Activation by Heat. 



The foregoing results show that the process, whatever its 

 nature, which is initiated in the mature unfertilized starfish egg 

 by temperatures of 30° to 36°, and which brings the egg into a 

 condition to form membranes cleave, and develop, proceeds 



