DEATH AND PROLONGATION OF LIFE IN THE EGG 205 



On the fourth day all the eggs which had not been treated at 

 all or had only been treated with the hypertonic solution were 

 dead. Those eggs that had been treated with both the hyper- 

 tonic and the propionic acid were developing and alive. 



This experiment was repeated quite often with the same result. 

 It proves that the corrective effect of the hypertonic solution is 

 irreversible and remains in the egg as long as it lives. 



5. One word should be said in regard to the fact that the expo- 

 sure of the eggs to hypertonic sea water which leads in Arbacia 

 iquite frequently to the origin of larvae, behaves so differently in 

 the eggs of S. purpuratus. The writer has repeatedly pointed 

 out this difference. His recent investigations have led him to 

 think that this is due to a typical difference in the reactions of 

 the eggs of the two species to the influence of the hypertonic 

 solution. In both species the eggs of only part of the females 

 can be induced to develop by the treatment with the hypertonic 

 solution alone, but the number of females with susceptible eggs is 

 much greater in Arbacia than in S. purpuratus. This year the 

 writer has investigated what constitutes this difference in the 

 behavior of the eggs of different females of purpuratus and found 

 the following fact. The eggs of different females were treated 

 with the same hypertonic solution at the same temperature and 

 for the same time. The eggs of the majority of the females be- 

 haved as described in the preceding chapter of this paper. The 

 eggs of some of the females of purpuratus developed into larvae 

 through the mere treatment with a hypertonic solution. The 

 difference between the two groups was this. The eggs which 

 developed formed somewhat atypical membranes (gelatinous 

 films), those that did not develop formed no membranes. The 

 membrane formation did not necessarily occur while the eggs 

 were in the hypertonic solution but often considerably later, 

 while the eggs were already beginning to segment. Those eggs 

 which had begun to segment but did not form the atypical mem- 

 brane stopped developing and went back into the resting stage 

 again. Those which formed membranes went on developing into 

 larvae. The specific difference between the eggs of different 

 females is therefore a difference in the facility with which the 



