1898.] BKBEDING OP THE DEAGONET. 305 



YI. The Soluble Pigment and the Palatahility . 



The yellow colouring-matter, already noticed as diffusely present 

 in the yellow bands of the fully-differentiated and breeding male, is 

 very readily soluble soon after death. Francis (' Nature,' xiii. 1875, 

 p. 167) has recorded the existence of a bluish-green pigment in 

 the Australian Wrasses Odax and Labrichthys, which is soluble 

 (presumably after death) in (fresh) water and sea-water. It is 

 nitrogenous and is destroyed by heat, chlorine, acetic acid, alkalies, 

 ammonia, and alcohol ; precipitated but not destroyed by sul- 

 phuric acid ; bleached by light. The yellow pigments of various 

 fishes studied by Cunningham and MacMunu appear to have been 

 less soluble, and these authors note that Francis's observations 

 have not been confirmed. A bluish-green colouring-matter is 

 certainly freely extracted from many European Wrasses in weak 

 formaldehyde, but I have never tested its solubility in water alone. 

 In Callionymus the yellow pigment is not given off in perceptible 

 quantity during life, but very soon after death it readily dissolves 

 out in fresh water, sea-water, dilute formaldehyde, glycerine, or 

 alcohol without change of colour. Ether extracts an ochre- 

 coloured solution ; mercuric chloride changes the yellow parts to 

 brick-red and extracts a solution of similar colour. Chloroform 

 extracts no colour. A strong aqueous solution is not affected by 

 heat nor by alcohol, is intensified by the addition of ammonia, 

 becomes colourless with acetic acid, and much more rapidly with 

 hydrochloric acid. The colour bleaches very rapidly in fight. 



The female has no yellow markings and no diffuse pigment, 

 but a similar yellow colouring-matter is extracted in small quantity 

 by alcohol from the chromatophores. Water appears to im- 

 mediately extract only the diffuse pigment, and therefore has no 

 effect on the female or young male. 



A strong aqueous solution of the yellow fi'om males has an 

 odour resembling that of an acrid cucumber. The same smell is 

 perceptible in the fish as a whole, and, to some extent, in both sexes. 

 The solution has a subacid taste, not particularly disagreeable, 

 but causes a prolonged irritation of the salivary glands. The same 

 results are experienced if one chews a bit of the second dorsal 

 fin of the male. The mucus can be easily obtained by irritating 

 the fish. It is tasteless and non-irritant, so that the offensive 

 properties clearly belong to the colouring-matter '. It has been 

 shown that the yellow pigment is most abundantly present at the 

 commencement of the breeding-season and subsequently fades to 

 a great extent. The manner of its disappearance requires explana- 

 tion. Considering the nature of pigments generally, it seems 

 improbable that the yellow matter is re-absorbed by the blood- 



1 I have not fully investigated the epidermal glands. It is possible that 

 some of these may secrete the irritant fluid. If so, it accompanies the diffusion 

 of the yeUow pigment ; but as the structure of the epidermis seems constant 

 and no irritant matter is discharged by young examples, it is much more 

 probable that the diffused yellow pigment is actually the seat of the irritation. 



Prog. Zool. Soc— 1898, No. XX. 20 



