ADJUSTMENT OF FLATFISHES 445 



and those which have been deprived of their sight experimentally, 

 cease to adjust themselves to the shade of their background. 



Certain of my own fishes which failed to respond adaptively 

 to changes of bottom were found to have become diseased in one 

 or both eyes, although, as has been stated, some of the most refrac- 

 tory individuals had not lost their sight. One of the fishes, both 

 of whose eyes were affected, acquired a peculiar appearance which 

 was not noted in any normal specimen. It assumed a rich brown 

 color, with specks of orange, the whole effect being much more 

 decorative than the somber hues ordinarily displayed by this 

 species. Another specimen, one of whose eyes had already become 

 blind, took on almost precisely the same appearance after I 

 had cut the optic nerve of the sound eye. In both cases the fishes 

 remained conspicuously out of harmony with the gravel or sand 

 on which they were kept. 



My most complete experiments in blinding fishes were later 

 made upon Lophopsetta, but a few w^hich were made with Rhom- 

 boidichthys deserve recording. It was at first my endeavor to 

 cover the eyes with some opaque coating, without thereby causing 

 any injury.^^ This proving impracticable, I next tried the effect of 

 searing the corneas with a red-hot platinum wire. The results, 

 with specimens no. 10 and 11, are detailed in the next paragraph. 

 The effect of cutting the optic nerve has already been described 

 for one specimen^^ I w^ill add that this fish was subsequently kept 

 for 22 days upon a white marble bottom. A shght paling was noted 

 at first, and this, as subsequent experiments showed, might have 

 occurred equally well on any bottom. Thereafter, no change 

 was noted, and the fish remained fairly dark as long as kept under 

 observation. 



One result of blinding, manifested in two of the foregoing speci- 

 mens, is of peculiar interest. Specimen no. 10, which had been 



" Mixtures of lampblack with certain fatty substances were tried, but it was 

 found that these would not adhere for more than a very few minutes. 



■"^2 Aside from the resulting loss of sight, it is probable that there is a distinct 

 shock effect from the cutting of the optic nerves. Thus specimen no 10 (see below), 

 when in a pale condition after the searing of the corneas, turned dark immediately, 

 upon the cutting of the optic nerves, and this dark condition presisted until the 

 death of the fish four days later. 



