1899-1900.] Dr Noel Paton and Mr Newbigin on Salmon. 53 
seemed of interest to compare the pigment of such Crustacea with 
the colouring matter of the muscles and ovaries of the salmon. 
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 annulicornis and Hippolyte spurifrons , and also large 0 
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) these 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 sufficient amount for detailed investigation. It 
especially recalls the pigment of the salmon in its close association 
with fat. 
