Reprinted fiom THE JOURNAL OF BIOLOGICAL CHEMISTRY, VOL. XIV, No. 5, 1913, 



AN IMPORTANT CHEMICAL DIFFERENCE BETWEEN 



THE EGGS OF THE SEA URCHIN AND 



THOSE OF THE STAR-FISH. 



BY A. P. MATHEWS. 



(From the Marine Biological Laboratory. Woods Hole.) 



(Received for publication, April 21, 1913.) 



The eggs of the sea urchin, Arbacia punctulata, differ markedly 

 in their physiological properties from those of the star-fish, Asterias 

 forbesii. The sea-urchin egg is remarkably stable, resistant to 

 oxidation, has a very low rate of respiration and is not easily 

 stimulated to artificial parthenogenesis; the star-fish egg, on the 

 other hand, is, after maturation, very easily oxidized, has a rapid 

 rate of respiration, forms sulphuretted hydrogen when mixed with 

 sulphur, is easily destroyed by oxygen, easily liquefied by heat 

 and is easily cytolyzed by anesthetics. It is readily, even by shock, 

 caused to develop parthenogenetically. Moreover after matura- 

 tion a steady growth of the nucleus takes place, whereas in Arbacia 

 the nucleus after maturation remains of a very small size. 



Five or six years ago I found an important chemical difference 

 between these eggs to be that cholesterol was lacking in the star- 

 fish egg, but present in some quantity in that of the sea urchin. 

 In view of the relation of cholesterol to hemolysis this observation 

 offers a possible explanation of the great ease of cytolysis of the 

 star-fish egg as compared with the sea-urchin. 



The eggs "were pressed from the ovary through cheese-cloth to 

 remove the connective tissue, and the mass then extracted three 

 times with a large amount of 95 per cent alcohol, boiling for one 

 hour each time, and then once with boiling ether. The united 

 extracts were evaporated on the water bath, the residue extracted 

 with ether repeatedly, filtered from insoluble substances, and the 

 ether poured into acetone. The fat and cholesterol remain in 

 solution; the lecithin is precipitated. The acetone filtrate was 

 evaporated to dryness, the oily residue saponified with alcoholic 



465 



THE JOURNAL OF BIOLOGICAL CHEMISTRY, VOL. XIV. NO. 5. 



