FERTILIZATION REACTION -IN ECHINARACHNIUS PARMA. 



47 



membranes in highly successful cases. Such eggs mixed with 

 sperm do not develop though the membranes be previously 

 removed as soon as formed. Thus, activation with butyric 

 acid is complete; eggs with membranes have undergone an 

 irreversible change. 



The Experiments. The method followed in these experiments 

 is simple. Eggs are exposed to n/io butyric acid in sea-water 

 (2 c.c. of acid plus 50 c.c. sea-water) and removed to 250 c.c. of 

 normal sea-water at five second intervals; these dishes comprise 

 Series A. From the dishes of series A eggs are removed, shaken 

 as soon as membranes are formed, and inseminated with fresh 

 sperm suspension; thus, series B is established. Samples of 

 eggs from each of the A dishes inseminated without shaking off 

 the membranes make up series C. The membranes formed in 

 series A and later the cleavages in B and C are recorded ; B and 

 C dishes are then gently washed in fresh sea-water and set aside 

 for study of the development during the next twenty-four hours. 



The experiment of July 9 is typical: 10.00 A.M. 6 dishes each 

 with 250 c.c. of sea-water to which eggs are removed after ex- 

 posure to butyric sea -water after 30, 35, 40, 60, 120 and 180 

 seconds (series Ai to A6). Samples from Ai to A 6 shaken and 

 inseminated (series B, i to 6). Series C samples from Ai to A6 

 inseminated without shaking. Table III. gives the results: 



TABLE III. 



"swimmers" 



64 to B6 and C4 to C6: cleavages very irregular; 



extremely abnormal exogastrulse, microgastrulae, blastulae with 



dense opaque interiors evidently due to abortive gastrulation. 



I have given this particular experiment because not a very high 

 per cent, of the eggs formed membranes. This ought, therefore 

 to be crucial, for since under-exposed eggs (i. e., those which are 



