80 INTRODUCTION. 



years before obtained similar results from a set of 

 somewhat extensive observations upon the Min- 

 now, Stickleback, Loach, and Perch. Any analysis 

 of these well-known experiments is unnecessary, 

 and hence we shall quote but a sentence regarding 

 the result. In the Stickleback the changes of colour 

 were still more remarkable than in the Minnow ; in 

 as much as they took place much more rapidly, and 

 even in a few minutes, and under the eye, th( 

 colours may be seen to fade and brighten according 

 to the nature of the vessel in which they are for the 

 time placed. The fine vermilion colour of the breast 

 almost disappears when placed in a white basin, and 

 the vivid colours are as speedily recovered on trans- 

 ferring the animals to a black glazed jar. The 

 sudden change, adds Dr. Stark, in relation to all the 

 fishes on which he experimented, is so striking, that 

 doubts of the identity of the animals might reason- 

 ably be entertained by one who vdtnessed the re- 

 sults without being aware of the circumstances 

 which led to them ; a few hours being sufficient to 

 produce all the phenomena. (Ed. N. Phil. J. ix. 

 327.) 



Upon the cause of this curious change, philoso- 

 phers, we believe, have hitherto thrown no light. 

 Mr. Couch, in a manuscript lately published by 

 Mr. Yarrell, seems to ascribe the change to the 

 eflfect of mental agitation. " The effect of passion," 

 remarks this intelligent Ichthyologist, " on the 

 colour of the skin of the genus Gasterosteus is re- 

 markable ; and in one specimen, under the influence 



