272 



RALPH S. LILLIE. 



Table IV. 



32' 



These results may safely be regarded as typical. Six other 

 similar series were carried out at this temperature. In two of 

 these the eggs were unfavorable or the treatment was applied 

 too late. In the four others — two in early June and two in late 

 August — the results were similar to the above, although fewer 

 eggs formed larvae; the optimum exposures ranged from 6 to 8 

 minutes, with respectively 20, 20, 40 and 50 per cent, of mature 

 eggs forming larvae. It will be noted that the optimum exposure 

 is approximately 8 minutes in five out of the six series in Table IV. 

 Different lots of eggs vary somewhat in the duration of this 

 optimum; thus in the series of June 25 half of the eggs formed 

 larvae with only five minutes' exposure and the optimum was 6 

 minutes, and on June 26 the eggs showed almost equally good 

 development with the 8- and the lo-minute exposures. In the 

 majority of series, however, there was a well-defined optimum at 

 7 or 8 minutes. 



The physiological effects following exposure to 32° vary in a 

 constant and highly characteristic manner with the duration of 

 the exposure. Eggs exposed for a period insufficient to induce 

 membrane-formation show no apparent change on return to 

 sea-water and later break down without development. Such 

 eggs, however, can be shown to have undergone some internal 

 change similar in kind to that following longer exposures; thus 

 if later they are again exposed to 32° they are found to require, 

 in order to induce favorable development, a shorter exposure 



