THE CAUSATION OF MATURATION IN THE EGGS 

 OF LIMPETS BY CHEMICAL MEANS. 1 



JULIAN MAST WOLFSOHN. 



In his experiments on the maturation of the eggs of the star- 

 fish [Asterias forbesii) 2 Dr. Loeb found that the eggs when re- 

 moved from the ovaries of the animal are in most cases immature, 

 but that if they come in contact with sea water, during the breed- 

 ing season they begin to maturate. The immature state is charac- 

 terized by a large, plainly-visible nucleus, which, during matura- 

 tion, becomes invisible. This process of maturation is completed 

 in from one to two hours after the eggs are removed from the 

 ovaries and placed in sea water. Only when the process of ma- 

 turation is completed is it possible to fertilize the eggs with sperm. 



Experimentation on the maturation of these eggs showed that 

 the chemical conditions necessary to cause or accelerate the ma- 

 turation processes are, that there must be present in the sea water 

 two substances, free oxygen and hydroxyl ions of a certain con- 

 centration. Dr. Loeb found further that if, upon becoming ma- 

 ture the eggs were not caused to develop by the addition of 

 sperm, then they died very rapidly. The change in the appear- 

 ance of the egg after death is very marked ; the living egg hav- 

 ing a light yellow color, after death it becomes black ; and where 

 in the living egg the protoplasm is homogeneous and somewhat 

 transparent, in the dead egg it becomes granular and opaque. 

 Thus it was found that in a culture that had been standing for 

 twenty-four hours, all the eggs that had remained immature were 

 alive, and all those that had matured were dead. This shows 

 that the mature eggs of the starfish die in the course of a few 

 hours, while under exactly the same conditions the immature 

 eggs remain alive. 



When the maturation is prevented artificially through lack of 



1 From the Herzstein Research Laboratory of the University of California. 

 2 Biological Bulletin, Vol. 3, No. 6, Nov., 1902. 



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