IIG Capt. G. E. II. Barrett-Hamilton on the 



In the Salmon it " occurs in th«^ muscle, the ovary, atid in 

 large amount in the liver," but " always in close association 

 with fat," upon which its "solubility seems to depend" 



(P- 161). 



As regards the significance ot the pigment, ^lis=? Newbigm 

 finds that two pigments of " similar or })erhaps identical 

 nature occur in the lobster, and in all probability in other 

 Crustacea." Hence Giinther suggested that the Salmon 

 derives its pigment directly from its food — n suggestion sup- 

 ported by the disappearance of the pigments while fasting, 

 iheir rcaj)))earance when tlie animal begins to take food, and 

 by their sjwradic a))pearance in certain Brown Trout, as if 

 they are dependent upon particular diet. Tiie difficulty is 

 that tlie Salmon does not feed directly upon Crustacea, but on 

 haddock, herrings, and similar fish. 



Mi?s Kewbigin could find no trace of the red pigment 

 either in the muscles or the viscera of the herring, and in her 

 opinion " it hardly seems probable that the amount of pigment 

 in the undigested food of the herring could be sufficient to 

 supply all the colouring-matter of tlie salmon's muscle " 

 (p. 161). Both muscle and viscera of herring, however, may 

 be made to yield traces of a yellow ])igment resembling that 

 obtained from the liver of the salmon. Hence tiie suggestion 

 that possibly " the salmon obtains the yellow pigment of its 

 muscle from food in association with fat and that j)art of this 

 jiigment is modified to form the red " *, a process which the 

 author compares to the transference of pigment to certain 

 caterpillars from their food f, and to the frequent presence of 

 yellow ])igment, evidently thus derived, in the fat of sheep 

 and cows. 



Ihis view brings with it another difficulty, viz. ''that 

 unless these three organisms can be shown to possess some 

 physiological peculiarity, then we are forced to the conclusion 

 that all yellow pigments in animals are derived from their 

 food — a conclusion for which there seems little evidence." 

 Further, if the presence of "pigment in the food is the only 

 condition necessary to produce piginented fat, it is difficult to 

 understand why such coloured fat should not be universal in 



* Poulton, Proc. Roy. Sor. London, liv. pp. 417-430; see also ' Natural 

 Science,' vol. \iii. pp. 98-100. 



t Later ill vest ipation.« by Mis.s Newbipin have disclosed the pret-ence 

 in certain Copepoda of a led lipochronie, which exhibits the same general 

 characters as the red pi}>nient of salmon, and especially recalls the latter 

 in its close association with fat. Unfortunately it was not obtained in 

 quantity sufficient to allow of detailed investigations (sfc '' Furtlier Inves- 

 tigations on the Life-History of the Salmon in Fresh Water,"" in Proc. 

 If. Sr,r-. i:<linburgh. Scss. lPOO-1900). 



