282 



RALPH S. LILLIE. 



and the time-relations of the exposures necessary for these 

 effects are closely similar with both methods. Table XI. 

 summarizes the results of five series of experiments with separate 

 lots of eggs. The eggs were exposed at normal temperatures 

 (20° to 22°) to an w/260 solution of butyric acid in sea-water 

 (50 c.c. sea-water plus 2 c.c. njio butyric acid), and portions 

 were transferred to normal sea-water at the intervals named. 

 The approximate proportion of mature eggs developing to free- 

 swimming larvae (blastulse and gastrulae) is given. 



Table XI. 



NI260 Butyric Acid.) 



The close parallelism between these experiments and those of 

 warming to 32° or 33° will at once be noted. With brief exposure 

 there is the same simple membrane-formation followed by break- 

 down without development; as the exposure is prolonged there 

 is a progressive increase in the proportion of favorably develop- 

 ing eggs up to an optimum ; then follow a decrease and eventual 

 failure to develop. More detailed observations show that the 

 rate and regularity of cleavage show a corresponding steady 

 improvement up to an optimum which is again followed by a 

 decline. 



The following observations show the condition of the eggs in 

 the second series of September i, at about four hours after the 

 treatment with butyric acid (Table XII.). 



The optimum time of exposure shows somewhat more vari- 

 ability in these series than is usually the case with exposure to 



