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 



