'hides" for fish. 125 



a moment. The next morning I found but few 

 outlying salmon in the tank, and on lifting 

 up the bridges was pleased to find that my 

 plan had succeeded, and that they found out 

 the bridges, and crept under them for shelter, 

 and there they lay all together like a lot of 

 rats under a barn floor. I remarked, more- 

 ovei", another result : before the fish went 

 under the bridges, they were comparatively 

 pale-looking things, with no colour in their 

 bodies ; a few short hours had made all the 

 difference, for three out of four of them had, 

 after they had been out of the light, acquired 

 the regular fish colour, and looked no longer 

 pale and miserable. 



I found subsequently that my experiment 

 had succeeded well ; for plates of zinc I 

 then substituted bits of common slate, such 



