208 JACQUES LOEB 



the eggs of the starfish. All these facts harmonize with the view 

 that both factors of fertilization are required for the life-saving 

 effect of fertilization. A similar situation exists in the case of 

 the eggs of some annelids. 



SUMMARY OF RESULTS 



1 . Since the unfertilized egg dies in a comparatively short time 

 while the act of fertilization saves the life of the egg, it was 

 proposed to find out which of the two factors of fertilization 

 is responsible for this effect, the membrane formation or the 

 corrective effect (produced in artificial parthenogenesis by the 

 hypertonic solution). In former experiments the writer had 

 shown that the artificial membrane formation alone hastens the 

 death of the unfertilized egg while the treatment of such eggs 

 with a hypertonic solution saves the life of the egg. This would 

 make it appear as if the second factor was solely responsible 

 for the life-saving effect of the act of fertilization. 



2. The writer had formerly shown that the treatment of the 

 egg with a hypertonic solution may precede the artificial mem- 

 brane formation. It is shown in this paper that if the unfertihzed 

 eggs of purpuratus have once been treated with a hypertonic so- 

 lution which in itself will not induce development they will 

 develop at any time after artificial membrane formation has 

 been induced. If the second factor is once imparted to this 

 egg it keeps it as long as it is alive. The hypertonic solution 

 induces an irreversible change in the egg. 



3. It is shown that the treatment with a hypertonic solution 

 alone does not prolong the life of the unfertilized egg. Eggs 

 treated in this way live no longer than unfertihzed eggs which 

 have not been treated at all. If in such eggs artificial mem- 

 brane formation is induced they will live indefinitely. For eggs 

 treated with a hypertonic solution the artificial membrane for- 

 mation becomes a live-saving act. 



4. It follows from this that for the prolongation of the life of 

 the unfertihzed egg both factors of artificial parthenogenesis, the 

 alteration of the surface as well as the second factor (usually 

 supplied by the treatment with hypertonic solution) are required. 



