in Animals as afforded by Observations on certain Salmonids. 281 



would indicate the analogies of all such, and, perhaps, of many 

 other phenomena. 



I believe a clue to such a state of things is to be found in 

 the nuptial changes of the anadromous salmonoid genus Onco- 

 rhynchus, the spawning of which I was recently fortunate enough 

 to observe in Kamchatkan waters. 



The facts in their broad sense have been described by Dr Guille- 

 mard 1 and are so well known that only the briefest recapitulation 

 of them is necessary. Each spring and summer the rivers of 

 Kamchatka are crowded with hosts of these salmon which leave 

 the sea for the purpose of spawning. There are several species, 

 and each has its own particular time for running, so that during 

 the whole summer the rivers are filled with individuals of one 

 or more species. On their first arrival these fish present no 

 remarkable coloration, being of a rather ordinary silvery or bluish 

 appearance. After they have been a short time in fresh water, 

 however, a great change comes over them. This manifests itself 

 in the appearance of very striking colours accompanied by a 

 strange increase in size or hypertrophy of certain parts of the 

 body. The colours and the parts affected are different in each 

 species. Most of the species become red, but especially 0. lycaodon 

 (Pall), locally known as the Red-fish. Others turn to a livid blue 

 or brown. All develop a formidable hooked snout, none more so 

 than 0. sanguinolentus (Pall.), the " Kisutch," and in one of them 

 0. proteus (Pall.), the Humpback, such an extraordinary hump 

 is produced on the back as to give rise to a belief among the 

 natives that this deformity has its origin in the frantic efforts of 

 the fish to ascend the rivers. 



Here then we have what, at first sight, appears to be an 

 abundant development of nuptial colours, together (in the case 

 of the snout) with a most efficient weapon wherewith to fight 

 a rival male 2 . A closer examination of the facts shows, I think, 

 that this is not all. 



In the first place the alterations, whether of colour or of form, 

 are not confined to one sex, but are (as far as we know) 

 developed in both. In the second place the fish when thus 

 affected are most obviously out of condition. There is in their 

 case no heightening of the silvery glancing colours of health, 

 but a replacement of them by utterly different sickly or livid 

 hues. The colours, and also the strange unnatural looking hyper- 

 trophy of snout or dorsal region are indeed merely the outward 

 symptoms of what I suggest is a pathological condition, in the 



1 See The Cruise of the Marchesa, Vol. i. Chap. vi. 



2 The facts were thus interpreted in the latter case by J. K. Lord (The Naturalist 

 in Vancouver Island and British Columbia, 1866, i. pp. 40 — 61), from whom Darwin 

 (The Descent of Man, 1871, n. pp. i and 5) borrowed them. 



