RECENT RESEARCH UPON SALMON 235 



inorganic substance known as guanin. The salmon has not 

 been many days in the fresh water before this brilliancy 

 becomes duller, until, after a sojourn of some weeks, the males 

 become ruddy brown and copper-coloured, the females sooty 

 grey and purplish. Fishermen usually regard this as the result 

 of the oxidising properties of fresh water, and indeed it is very 

 similar in effect to the tarnishing of silver. But this explanation 

 fails to account for the phenomenon exhibited after spawning, 

 Kelts rapidly use the dark tones assumed by gravid fish, and, 

 before they reach the sea again, become as white and silvery as 

 they were when they left it. It is probable that these changes 

 in skin colour are independent of external agents, and arise 

 from alterations in the circulatory system. In the higher 

 vertebrates, the skin colour or complexion is intimately 

 connected with the circulation ; so, in the salmon, it is 

 probable that when the blood stream is diverted from the 

 stomach to the growing ovaries, not only does the stomach 

 become functionless, but the effect is immediately seen upon 

 the skin. After the milt or ova are deposited, the blood 

 reverts to its normal course, the stomach begins to resume its 

 normal condition, and the skin recovers its brilliancy. That, 

 very roughly and briefly stated, is the conclusion to which 

 research has tended, although the reader is entitled to be 

 spared the physiological details upon which it rests, and also 

 the evidence for the transference of ruddy pigment in the 

 muscle of fresh-run salmon to the skin in the males and to the 

 ovaries in the females. 



Then arises the question — what is a *' well-mended kelt," 

 so well known to anglers ; a kelt, that is, which has 

 recovered not only its lustre, but, apparently, regained some 

 muscle } The process of " mending " has been well described 

 by Professor Miescher Ruesch : — 



How altogether different is the picture if we have the opportunity to 

 see the creature ten days, or, better, two weeks after spawning. The skin 

 is again bluish, shining and clear ; the ulcers cicatrised and healing, the 



