88 THP COLOURS OF ANIMALS 



concealed individuals. This is sufficiently explained 

 by the facts that the waters are carefully preserved, 

 and that the blindness only comes on when the fish 

 are large, and are therefore exposed to the attacks of 

 comparatively few enemies. 



Mr. Nicoll informed me that the black fish were 

 usually in very poor condition, and I was very anxious 

 to ascertain the kind of food which was still accessible 

 to them. We therefore caught two fine specimens 

 which were in fair condition. I opened them and 

 found their stomachs quite full of caddice-worms, 

 cases and all, together with a few fresh-water shrimps 

 (Gammarus), These animals are doubtless hunted by 

 scent and touch, while the insects on the surface of 

 the water can only be obtained by sight. 1 



Loss of power of varying colour in a chameleon 

 before death 



The changes which took place in a chamaeleon in 

 my possession probably show the dependence of the 

 power of adjustment upon the state of the nervous 

 system. In the summer, while the lizard was healthy 

 and had an abundance and variety of insect food, it 

 was dark-coloured by day, when it rested on some 

 dark branches or walked about in its shaded cage. 

 Placed upon a leafy branch in strong light it became 



1 Certain fish habitually seek their food by the olfactory and 

 tactile senses. See Bateson, I.e. p. 214. 



