102 Papers from the Department of Marine Biology. 



CHEMICAL NATURE OF THE GELATINOUS SUBSTANCE OF CASSIOPEA. 



The chemical nature of the jelly-like substance (reserve substance) 

 of various forms of medusae has been examined by several investigators, 

 but so far as I am aware nothing has been definitely established as to 

 the chemical nature of this puzzling structure. 



Krukenberg (1882) considers this substance to be composed of 

 protein material which is easily digested with either pepsin or trypsin 

 and splits off leucin, tyrosin, and other substances not identified. 

 Very recently Macallum (1903) published his extensive investigations 

 on the inorganic constituents of the medusae Aurelia and Cyanea, 

 and mentions in the text that "the jelly is constituted of an almost 

 infinitesimally minute network formed of a proteid." In another 

 place Macallum states that "it must be noted that the total amount 

 of proteid in Aurelia is very small, ranging between one-seventh and 

 one-eighth of 1 per cent of the total weight of the organism," but in no 

 place in the paper does Macallum mention either the kind of protein 

 present or give any analytical data to show how he determined the 

 quantity of this protein. There are also some chemical observations 

 of a qualitative nature made by Schulze in 1856 and by Schlossberger 

 in 1856. Vernon (1895), who made extensive observations on the 

 phenomena of respiratory exchange in various marine invertebrates, 

 thinks that "the solid organic constituents may not consist by any 

 means of pure proteid." 



From the above we see that the true nature of the jelly or ground 

 substance of the medusae is not determined; this makes it difficult to 

 interpret the various changes noted in the present experiments. It is at 

 once evident, however, that the solids can not be constituted as a whole 

 by the ordinary protein, since the latter usually yields nitrogen to the 

 extent of 12 to 18 per cent, contrasted with 3 per cent in the dried 

 Cassiopea. 



Even if we calculate the nitrogen in ash-free solids, the value rises 

 no higher than 6 per cent ; but this nitrogen value (about 6 per cent) is 

 interesting in view of the fact that it is the value found by Schloss- 

 berger (1856) for the chitinous substance. Although the nitrogen- 

 content in the solids alone is not adequate to show that we are dealing 

 with a chitin-like substance, yet recent investigations by Henze 

 (1908) on the identity of the framework of siphonophorse with chitin 

 and, further, the wide occurrence of chitin in numerous marine inver- 

 tebrates as shown by Irwin (see Armstrong, 1912) indicate that the 

 ground-substance of the medusae might be similar. If this supposi- 

 tion turns out to be true, its biological significance becomes at once 

 evident, since chitin is closely related to mucin, which in turn is closely 

 related to the cartilage of the vertebrate skeleton. 



