1 RALPH S. LILLIE. 



In each series the eggs show an optimum of activation with an 

 exposure of about 30 minutes. The differences between the 

 three series are not great ; in each series over-exposure (35 minutes 

 and longer) is followed by the complete breakdown and disin- 

 tegration of a large proportion of eggs; by next day nothing is 

 left of these eggs but a thin structureless residue ("ghosts"). 

 This dissolution is much more complete than that resulting 

 from moderate over-exposure to butyric acid at higher temper- 

 atures. It will be noted that the proportion of eggs developing 

 favorably with the optimum exposure is highest at 6 and lowest 

 at 2; i. e., the destructive effect is greater the lower the temper- 

 ature. 



The higher rate of activation in these experiments, as compared 

 with that observed at slightly higher temperatures (8 to 10), is 

 almost undoubtedly the expression of a summation of the two 

 separate effects of cold and butyric acid. This is indicated by 

 the results of exposure to normal sea-water at these temperatures. 

 On June 14 eggs were exposed, under the same conditions as 

 above, to normal sea-water at 2, 4, and 6. The result was a 

 typical though partial activation in each series; a large majority 

 of eggs not all formed membranes and underwent irregular 

 fragmentation and breakdown without further development. 

 In each series a considerable proportion of eggs (about one third 

 to one fourth) remained apparently unaffected, and later under- 

 went the usual postmaturational coagulation without membrane- 

 formation or development. Several other similar experiments 

 yielded similar results. The above durations of exposure are 

 evidently too brief for complete activation. With longer ex- 

 posures (about 6 hours) a few eggs may form larvae under these 

 or similar conditions. 1 Evidently low temperature alone may 

 initiate the activation-process; hence with cold and butyric acid 

 combined the rate of activation may be more rapid than with 

 butyric acid at the higher temperatures of 8 and 10, which by 



1 In Greeley's experiments (loc. cit., 1902) the best results were obtained when 

 the eggs were exposed, beginning three to four hours after the completion of matur- 

 ation, for six to nine hours to temperatures of 4-5. The highest proportion of 

 larvae obtained was 20 per cent.; usually only 1-2 per cent, of eggs formed larvae. 

 The period after maturation is completed is in general unfavorable for activation in 

 starfish eggs. 



