ACTIVATION OF EGGS OF SEA URCHIN. IOJ 



NaCl -f- KC1 + CaCl 2 . These eggs did not disintegrate during 

 the following night although they did not appear quite normal the 

 next day. The rest of the eggs remained in the m/2 NaCl -f 

 KC1 + CaCl 2 solution for twenty-four hours. When these 

 eggs were put into sea-water they did not disintegrate. To some 

 of these eggs sperm was added the next morning and about 

 20 per cent, developed. 



This experiment indicates that the nature of the membrane 

 and the cortical changes which activate the egg of purpuratus 

 are to a large extent determined by the solution into which the 

 eggs are put after the butyric acid treatment. If the eggs are 

 put directly into sea-water after the butyric acid treatment 

 they form the typical membrane and rapidly perish if nothing 

 else happens to them. The same may be the case if they are 

 transferred from the butyric acid solution into a neutral solution 

 of m/2 NaCl + KC1 -f- CaCl 2 for a short time (less than one 

 hour) and if they are afterwards transferred into normal sea- 

 water. But if they remain in the NaCl + KC1 + CaCl 2 

 solution for a number of hours they will as a rule not disintegrate 

 if put back into sea-water. 



A second experiment may be quoted. Eggs (that had been 

 washed three times in a neutral m/2 NaCl + KC1 + CaCl 2 

 solution) were put for one and a half to two and a half minutes 

 at a temperature of about 14 into 50 c.c. of the same solution -f- 

 I c.c. N/io butyric acid. From here the majority of the eggs 

 were transferred into a neutral solution of m/2 NaCl + KC1 

 CaCl 2 and the rest into sea-water. The latter formed normal 

 fertilization membranes and disintegrated the same day. Those 

 transferred into the neutral NaCl + KC1 + CaCl 2 solution 

 had all formed membranes which were at first separated from 

 the egg by a great distance. They were kept in this sol- 

 ution over night, and the next morning they were transferred 

 into normal sea-water. All looked normal except that the 

 membrane now formed a fine veil lying closely to the egg. 

 Some of these eggs were fertilized with sperm. They all seg- 

 mented and developed into swimming larvae. The others were 

 kept in sea-water without sperm to find out whether they would 

 now disintegrate or whether the effect of the butyric acid treat- 



