100 THE STORY OF FISH LIFE. 



and developed fins or membranes. If the 

 variations of these modifications are less notable 

 than the modifications of the epidermal structures 

 of birds, full compensation is found in the 

 marvellous range of brilliancy in the hues of the 

 skin which we have already discussed: 



The diff'erence in the size of the sexes of fishes 

 is a very noteworthy feature, and naturally one 

 of the first things which would attract our 

 attention in this connection. Thus, among what 

 are known as the "bony" fishes, e.g.: salmon, 

 perch, the females are larger than the males; 

 among some of the carp tribe the female is often 

 as much as six times as large as her mate ; some- 

 times, however, as in the cod, haddock, angler, 

 and cat-fish the males are larger, but only slightly 

 so. Occasionally, the female appears to be more 

 perfectly armed than the male; thus, among 

 certain rays which are armed with bucklers or 

 pointed scales, it is the female on which they are 

 found, the male being almost or completely 

 smooth. 



With the fishes as with the birds, the possession 

 of a mate seems to be accomplished in one of 

 two ways, conquest by battle, or conquest by 

 blandishment. 



One of the best known and most interesting of 

 the instances of conquest by battle is afforded us 

 in the salmon of our rivers. The male salmon 

 fight ferociously amongst themselves, the strongest 

 driving away all rivals. So serious are these 

 engagements that Mr Darwin was informed, on 

 one occasion, as many as 300, all males with 

 one exception, were found dead in the Tyne 



