of the Fishery Board for Scotland. 



85 



During last summer, Sir John Murray sent to the Laboratory of the 

 Royal College of Physicians collections of Crustacea obtained by tow- 

 netting in Loch Fyne, in order that the pigments might be investigated. 

 The Crustacea sent were all of a red colour, and are believed to constitute 

 the chief food of the herring. The object of the investigation was to find 

 what relation, if any, the pigments of these Crustacea bear to those of 

 the salmon. 



When received, the Crustacea were preserved in methylated spirit or in 

 alcohol of various strengths. In no case was the preserving fluid 

 markedly coloured, most of the pigment being still retained by the 

 organisms. As to the Crustacea sent, there were separate bottles of 

 Pandalus annulicomis and Hippolyte scutifrons, and also large bottles 

 labelled "contents of tow-net in Upper Loch Fyne." These last contained 

 chiefly copepoda intermixed with colourless organisms such as Sagitta, 

 and also various Euphausidae, species of Hippolyte, etc. The larger 

 Crustacea were picked out from among the copepoda, and the pigments 

 investigated in two sets — (1) those of the copepoda, (2) those of the other 

 Crustacea. 



1 . The copepoda contained a large amount of fat in which the pigment 

 was dissolved. It was found possible by squeezing to extract from their 

 bodies drops of fat deeply coloured by the reddish pigment. Both fat 

 and pigment dissolve in boiling methylated spirit ; but on cooling, the 

 coloured fat separates out at the bottom of the vessel. Both fat and 

 pigment dissolve readily in ether, which is thus a much better solvent 

 for the pigment than alcohol. When the fat is saponified either by 

 heating with an alcoholic solution of caustic soda, or by adding metallic 

 sodium to a solution in ether, a red soap is formed from which the 

 pigment may be obtained after treatment with acid. A small amount 

 of a yellow pigment remains in solution in the caustic solution after 

 saponification, as in the case of the salmon pigment. 



The red pigment is a lipochrome, and exhibits the same general 

 characters as the red pigment of the salmon, but it was not obtained in 

 suflicient amount for detailed investigation. It especially recalls the 

 pigment of the salmon in its close association with fat. 



2. The pigments of the other Crustacea sent closely resembled those of 

 the Norway lobster. The most distinct difference from the copepoda 

 lies in the fact that the red pigment is chiefly found in the chitinous 

 cuticle and in the epidermis ; the occurrence of a coloured oil was not 

 obvious. 



