Mr Shaw's Experiments on the Fry of the Salmon. 173 



some influence on the progressive growth of the fish by which 

 they are respectively inhabited, I still believe the final result 

 will prove almost the same. 



Before concluding this paper, it may not be altogether out 

 of place to detail the particulars of a few simple experiments 

 made to elucidate a very extraordinary phenomenon connected 

 with this fish, namely, the fact of its changing colour under 

 certain circumstances.* In the course of my visits to the expe- 

 rimental pond, which were as frequent as other duties would 

 permit, Ihad often observed, that, while the little fish remained 

 stationary in any particular part of the pond, they were always 

 found to be of a colour corresponding to the colour of the bot- 

 tom, and when they removed to any other part of a different 

 colour, that, after resting on it for a few minutes, they gradu- 

 ally assumed a corresponding hue. Wishing, therefore, to 

 prove the fact of this assimilation by actual experiment, I pro- 

 cured two large earthenware basins, one nearly white inside, 

 the other nearly black. I then placed a living fish in each, 

 while at the same time I kept up a constant supply of fresh 

 water in them. The fishes were of their natural colour when 

 first placed in the basins ; but they had not remained there 

 more than four minutes till each had gradually assumed a co- 

 lour nearly approaching to that of the respective basins in which 

 they were placed. I next took the fish out of the white basin 

 and placed it in the black one, and the fish which was in the 

 black basin I placed in the white, and the results were uniform- 

 ly the same, — the fishes changing according to the colour of the 

 surface over which they were placed. I next placed both fishes 

 in one basin, when the contrast for a short time was exceeding- 

 ly striking. With the view of ascertaining what effect the 

 light had in producing this extraordinary change, I next al- 

 lowed the fish to remain in the white basin so long as effectual- 

 ly to acquire the light tint, when I excluded the light from 

 them altogether by covering the basin with a thick mat, and 

 on removing it a few minutes afterwards, I found the fish were 



* Since these observations on the changing colour of the fish were put in 

 types, my attention has been directed to an interesting paper on the same 

 subject in reference to the minnow, stickleback, and perch, contributed by Dr 

 Stark to the Number of this Journal for October 1030. 



