IO4 JACQUES LOEB. 



or NaCN solution. If they are first transferred into normal 

 sea-water and then after fifteen or thirty minutes later are 

 transferred to the cyanide solution nothing may happen to them 

 as long as they remain in the cyanide solution (unless the HCN 

 evaporates) but they will disintegrate when put back into normal 

 sea-water. From this we must conclude that in the sea-water 

 the processes started in the alkaline solution will continue and 

 the egg behaves as if it had been overexposed to the hyperal- 

 kaline solution. 



Somewhat similar experiments were made with the eggs of 

 Arbacia which had been treated with butyric acid. When such 

 eggs were put over night into the cyanide-sea-water immediately 

 after the artificial membrane formation they did not as a rule 

 disintegrate when put back into normal sea-water but could be 

 fertilized afterwards. The writer is, however, not certain that 

 the phenomenon of reversibility is as constant here as in the 

 case of the alkali treatment. 



The writer pointed out that the explanation for this phenome- 

 non could probably be found if we compare the behavior of the 

 eggs of Arbacia with that of eggs of purpuratus under similar con- 

 ditions. If we cause the production of a butyric acid membrane 

 in the egg of purpuratus the activation of the egg is usually irrever- 

 sible. In the egg of purpuratus the membrane which is formed 

 under the butyric acid treatment is very tough and is separated by 

 a wide area from the protoplasm, while in the egg of Arbacia the 

 membrane consists often only of a fine gelatinous film which lies 

 tightly around the egg. The writer concluded from this that there 

 may be a quantitative if not a qualitative difference in the 

 amount of change produced by the butyric acid treatment in 

 the cortical layer of the two kinds of eggs; in the egg of Arbacia 

 where this change is quantitatively smaller the activation is 

 reversible, while in the egg of purpuratus where the change is 

 quantitatively larger (and possibly also qualitatively different) 

 it is irreversible (Loeb, "Artificial Parthenogenesis and Fertiliza- 

 tion," Chicago, 1913, p. 286). 



2. This idea is further supported by the curious phenomena 

 of reversibility in the eggs of Strongylocentrotus purpuratus. 

 When one tries to induce artificial parthenogenesis in the eggs 



