194 BRITISH FRESH-WATER FISHES 



(see page 158). A more probable explanation of the change 

 of skin colour which takes place after the salmon enters fresh 

 water will be submitted in the next chapter. In most 

 teleosteous fish the carps and pike, for instance the 

 beauty of colour culminates at the spawning season, as if 

 the different sexes took pleasure in the brilliancy of each 

 other. It is difficult, for instance, to imagine a female 

 stickleback of so phlegmatic a nature as not to derive 

 excitement from the bridal raiment of her spouse. But 

 salmon, male and female, so far from acquiring enhanced 

 comeliness at this critical season, become positively unsightly. 

 The male turns to a deep coppery brown ; the burnished 

 silver of his mate is deeply tarnished with exactly the same 

 tints as sulphurous fumes impart to the real metal. Her 

 snowy throat and underparts are smeared and stained with 

 the same sooty hue, and her once perfect form distended by 

 the swollen ovaries. Both sexes lose their crispness to the 

 touch, and become covered with slime. 



As if this disguise were not enough, the male assumes 

 as it were an ugly mask. When salmon of less than 10 Ib. 

 or 12 Ib. in weight leave the sea the heads of the two sexes 

 are indistinguishable from each other ; * but as the milt 

 grows in the male so do his snout and lower jaw, and at 

 the end of the lower jaw a knob grows upon the upper 

 edge of the mandible, forming a pronounced hook, which, 

 in old males, fits into a recess in the snout when the mouth 

 is closed. This characteristic hook is neither cartilaginous 

 nor bony, but is formed entirely of cutaneous connective 



* I am quite aware that experienced fishermen profess to distinguish 

 between newly-run male and female fish by the shape of their jaws, but I 

 have adduced evidence on page 237 to show that it is impossible to do 

 so early in the season, before the generative apparatus of the fish has 

 advanced towards maturity. It is difficult, perhaps impossible, to convince 

 fishermen of this, and indeed in very old males the base of the temporary 

 hook formed on the mandible becomes bony, and the jaws remain longer 

 than those of females, thereby affording a permanent indication of sex. 



