ii4 Artificial Parthenogenesis 



shortly before disintegration sets in. The writer has 

 studied this phenomenon in the unfertilized eggs of 

 purpuratus and found that only the eggs of certain 

 females show this cell division before disintegration 

 and that the cell division is preceded by an atypical 

 form of membrane formation; the eggs surrounding 

 themselves by a fine gelatinous film comparable to 

 that produced in the egg of Arbacia by a treatment with 

 butyric acid. It is difficult to state what induces the 

 alteration of the surface in the eggs that lie so long in 

 sea water. It may be due to the C0 2 formed by the 

 eggs — since we know that C0 2 may induce membrane 

 formation — or it may be due to the alkalinity of the 

 sea water or to a substance originating from the jelly 

 surrounding the eggs. It was found that if such eggs 

 are kept without oxygen their disintegration (and cell 

 division) will be delayed considerably. The presum- 

 able explanation for this is that the lack of oxygen pre- 

 vents the internal changes underlying cell division and 

 thus prevents the disintegration of the egg. The direct 

 proof that an egg in the process of cell division is more 

 endangered by abnormal solutions than an egg at rest 

 has been furnished by numerous observations of the 

 writer. He showed in 1906 that the fertilized egg of 

 purpuratus dies rather rapidly in a pure m/2 NaCl 

 or any other abnormal isotonic solution, while the unfer- 

 tilized egg can live for days in such solutions. 1 In 



1 Loeb, J., Biochem. Ztschr., 1906, ii., 81. 



