CHEMICAL NOTES ON THE EGG CAPSULES OF TWO 



SPECIES OF SHARKS 



LOUIS HUSSAKOF and WILLIAM H. WELKER 



{Laboratory of Biological Chemistry of Columbia University, at the College of 

 Physicians and Surgeons, New York) 



(With plate 4) 



I. INTRODUCTION 



Various types of sharks deposit eggs which remain in the water 

 for a considerable time — in some forms for nearly a year — until the 

 young are hatched and capable of independent existence. These 

 eggs are provided with very resistant egg-shells, or " tgg capsules," 

 composed of material capable of withstanding water action for a 

 long period. The capsules consist of an elastic shell, yellowish- 

 brown, reddish-brown, or chocolate in color, semi-translucent, and 

 somewhat horn-like in appearance. The form of egg capsule varies 

 with the species; one of the commonest is that shown in figure i, 

 and a rarer form is that shown in figure 2. 



The chemical composition of these egg capsules has apparently 

 never been investigated. We have been unable to find any chemical 

 references to them. Superficially their substance is suggestive of 

 keratin; but the tests which we have made, as shown in this paper, 

 indicate that this substance is distinct from keratin. 



The observations which we desire to record in this preliminary 

 communication have to do with both the tgg capsules and the color- 

 ing matter which they contain. 



II. MATERIAL STUDIED 

 We employed the egg capsules of two very different sharks: 

 (i) the skate {Raja erinacea) and (2) the Port Jackson shark 

 {Heterodontus philippi). The former species is quite common on 

 the north shore of Long Island, where its empty, blackened and 

 weatherbeaten capsules are washed ashore with other detritus. A 



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