40 E. E. JUST. 



"refertilize" (see older work of Driesch and the important work 

 of Wilson on Cerebratulus) . The present paper reports results 

 of an attempt to determine whether or not in Echinarachnius 

 eggs activation by butyric acid is complete in the sense that it is 

 complete when membranes form after the initial stage in the 

 fertilization process. If we assume that activation is complete 

 in eggs that have formed membranes after butyric acid then 

 hypertonic sea-water exposure should give the best development 

 with these eggs. Any other assumption is absurd unless the use 

 of butyric acid is unnecessary, when used with hypertonic sea- 

 water, for the best type of development. Again, on the assump- 

 tion that with membrane formation following butyric acid the 

 activation is complete, as it is in fertilization, the egg should 

 react on insemination as do fertilized eggs or fragments thereof. 

 The observations show that after butyric acid treatment under 

 optimum conditions eggs form membranes (Part II.); and that 

 in such eggs activation is complete since with hypertonic treat- 

 ment they give rise to cleavages, gastrulae and plutei of a high 

 degree of normality, and since they fail to develop after insemi- 

 nation (Part III.). 



II. ACTIVATION OF ECHINARACHNIUS EGGS BY BUTYRIC 



ACID. 



Eggs of Echinarachnius if properly exposed to butyric acid 

 in sea-water are activated and so form membranes that are 

 indistinguishable from those formed following insemination. 



A. Optimum Exposure to Butyric Acid. 



Without the experiments being cited it may be said that by 

 using various mixtures of butyric acid in sea-water the best 

 mixture was found to be 2 c.c. of w/io butyric acid plus 50 c.c. 

 of sea-water. The optimum exposure for this mixture discovered 

 by removing samples of eggs from the butyric mixture at five 

 second intervals, is thirty-five seconds. In some cases eggs 

 were exposed for sixteen minutes. 



The following experiment of July 8 is cited as typical: 9:50 

 A.M., 15 dishes each with 250 c.c. of sea-water. 10:18 A.M., 

 2 c.c. n/io butyric acid plus 50 c.c. of sea-water thoroughly 



