SPECKLED TROUT. 123 



little stickleback goes through an elaborate 

 courtship, and I have myself watched trout 

 which seemed to me as obviously love- 

 making as any pair of turtle-doves I ever 

 saw. In their early life salmon fry and 

 young trout are almost quite indistinguish- 

 able, being both marked with blue patches 

 (known as ' finger-marks ') on their sides, 

 which are remnants of the ancestral colour- 

 ing once common to the whole race. But 

 as they grow up, their later-acquired tastes 

 begin to produce a divergence, due originally 

 to this selective preference of certain beauti- 

 ful mates ; and the adult salmon clothes him- 

 self from head to tail in sheeny silver, while 

 the full-grown trout decks his sides with the 

 beautiful speckles which have earned him 

 his popular name. Countless generations of 

 slight differences, selected from time to time 

 by the strongest and handsomest fish, have 

 sufficed at length to bring about these conspi- 

 cuous variations from the primitive type, 

 which the young of both races still preserve. 



