SEEN WITH THE EYE OF A FISH = 35 
limpid brook and gurgling stream from the Malay 
Archipelago to the West Coast of Ireland. Probably the 
loach depends for his survival over so wide a distribution 
on exceptional powers of adapting his markings to new 
surroundings. As an illustration of the usual markings 
on a stone loach, look at the middle photograph on 
the plate that precedes p. 31. 
Next look at the skins of two loach on the accom- 
panying plate. The first is a photograph of the skin 
of a loach caught in a brook where the bottom was 
muddy; the second came from the same brook several 
miles higher up, where the water rippled over gravel. 
In the first the pigment cells have increased in 
number, and, instead of the usual spotty appearance of 
the skin, the colour is much more uniform, in order that 
this fish may the better be concealed on a dark, dirty 
bottom. In the second the spotty appearance is exag- 
gerated, and even the back has quite clear spaces upon 
it—an arrangement of pigment that is more suitable to 
a gravelly bottom. 
In some fish the markings invariably change during 
the life of an individual. This is so in the pike. The 
body of the young pike is crossed by several brilliant 
yellow bars, and lying hidden amongst the reeds these 
bars protect him in much the same way as the bars 
protect the perch. He can thus catch his prey and also 
escape falling a victim to his enemies. 
When the pike is nine inches or more in length, the 
yellow pigment cells disappear at regular intervals along 
