SEEN WITH THE EYE OF A FISH 37 
A few brilliant fish, however, are found in northern 
waters, the most noticeable being the wrasses. Among 
our own freshwater fish brightness is given to roach, 
rudd, perch, by their brilliant red fins. The brilliant 
fins may serve as a means by which these gregarious 
fish recognise each other, but recently I have noticed 
that in the spring-time the young shoots and roots of 
the common rush are exactly the red of the roach, rudd 
and perch fins. At this time of the year the fish spawn 
among the reeds, and there is no doubt that the red fins, 
which at this season become still more brilliant, assist 
in concealing the fish, just when concealment is most 
required. 
Bright colours also occur among fishes other than 
for concealing purposes. For example, the male becomes 
bright in order to make himself attractive to the opposite 
sex. 
Though fish depend mainly upon concealing colora- 
tion for success in the struggle for existence, we must 
not forget that agility, size, weapons of defence, and 
warning attitudes all play their part. 
Weapons of defence frequently take the form of 
some modification of the fins. In the ruffe, for example, 
the rays of the first dorsal fin end in formidable spines. 
When this fish was photographed, he invariably erected 
his fin as I approached the tank, as shown in the illustra- 
tion. 
Many fish, in addition to being armed, take up 
terrifying attitudes when alarmed, and thus warn off 
