184 THE COMMERCIAL SEA FISHES OF 



turbance could occur, seven out of fifteen were noticed 

 endeavouring to force the eye round the wrong way by 

 lying down on the opposite side. But all the seven soon 

 died, and this may account for the comparative scarcity of 

 reversed flat fishes. He also observed that the presence of 

 light on all sides failed to arrest, or even to delay, the 

 transfer of the eye, and the consequent change in the colour 

 of the under side, which invariably became white with 

 advancing age, when that organ passed over to the upper 

 surface. Thus it would appear that the absence of light is 

 not the primary or sole cause of the want of colour on the 

 under side of the flat fishes. 



While the eye is progressing from the one side of the 

 head to the opposite, where it is to find its final resting- 

 place, its course is occasionally arrested, and it may remain 

 permanently stationary on the upper surface of the head, 

 and this is commonly but not invariably seen in what are 

 known as " double flat fishes," or those coloured on both 

 sides. Double fishes have been observed in flounders, 

 turbot, plaice, soles, &c., and they are seen to swim ver- 

 tically, and to be more frequently found near the surface of 

 the water than those which progress in a normal manner. All 

 who have eaten these double flat fishes know how they are 

 most deservedly held in greater estimation for the table 

 than others which have an uncoloured as well as a coloured 

 side. There are likewise albinos, or those which are un- 

 coloured or nearly white on both sides (being almost or 

 quite double albinos), and still retaining their normal form ; 

 but in some that have been carefully examined no sexual 

 organs could be detected. 



In the majority of albino examples only patches or 

 portions of the body are thus affected, and it has been 

 suggested whether such may not, at least occasionally, be 



