150 CARL RICHARD MOORE. 



cytolize even more rapidly than in cases where membranes have 

 been produced. Practically all pigment diffuses from eggs so 

 treated, when allowed to stand, within a very few hours; they 

 will, many times, have almost completely disintegrated when the 

 first signs of cytolysis appear in eggs provided with membranes. 

 Furthermore, what evidence of membrane production have we 

 when the membrane is not visible? We have no reason to 

 doubt that partial fertilization, at least, is possible in instances 

 where no membranes appear following the acid treatment; mem- 

 brane production has not been initiated. Activation has, at 

 best, been only partially effected; the reactions may have been 

 started but they were not completed. It behooves us to look a 

 little more closely at the process of the butyric acid treatment. 

 The best method for causing membrane production in the 

 egg of Arbacia is the famous butyric-acid method developed 

 by Loeb. But, as all who have used it know, great care must 

 be exercised, to obtain the best results. As Loeb has pointed 

 out different lots of eggs respond very differently to essentially 

 the same treatment. But if these facts are borne in mind very 

 good results may be obtained. The eggs used in my experiments 

 have always been washed from two to four times before treat- 

 ment. Unwashed eggs do not usually give good results; many 

 eggs do not produce membranes. One variable feature in ob- 

 taining good membranes is the length of time the eggs are allowed 

 to remain in the acid. This is probably dependent somewhat 

 upon temperature as well as upon the conditions of the individual 

 eggs. In some of my experiments I have obtained the best 

 results (highest percentage of eggs producing membranes and 

 membranes appearing normal in size) from exposures lasting 

 only fifteen seconds; at other times longer exposures give better 

 results. This sometimes is obtained at twenty-five to thirty 

 seconds but usually it is near twenty seconds that the better 

 results are obtained. Acidity is a factor that must be considered : 

 a very slight amount of acid after the transfer prevents the 

 reaction from being complete. Thus I have found in some 

 cases that a solution into which the eggs have been removed 

 following the acid treatment, that is as slightly acid as /i,6oo 

 would entirely prevent membrane production. 



