Chap. XII. FISHES. 19 



evidence on this head. We can see that one sex will 

 not be modified through natural selection for the sake 

 of protection more than the other, supposing both to 

 vary, unless one sex is exposed for a longer period 

 to danger, or has less power of escaping from such 

 danger than the other sex ; and it does not appear that 

 with fishes the sexes differ in these respects. As far as 

 there is any difference, the males, from being generally 

 of smaller size, and from wandering more about, are 

 exposed to greater danger than the females ; and yet, 

 when the sexes differ, the males are almost always the 

 most conspicuously coloured. The ova are fertilised 

 immediately after being deposited, and when this pro- 

 cess lasts for several days, as in the case of the salmon,^ 

 the female, during the whole time, is attended by the 

 male. After the ova are fertilised they are, in most 

 cases, left unprotected by both parents, so that the 

 males and females, as far as oviposition is concerned, 

 are equally exposed to danger, and both are equally 

 important for the production of fertile ova ; consequently 

 the more or less brightly-coloured individuals of either 

 sex w^ould be equally liable to be destroyed or pre- 

 served, and both would have an equal influence on the 

 colours of their offspring or the race. 



Certain fishes, belonging to several families, make 

 nests ; and some of these flashes take care of their 

 vouno; when hatched. Both sexes of the brio-htly- 

 coloured Crenilahrus massa and melops work together in 

 building their nests with sea-weed, shells, &c.^^ But the 

 males of certain fishes do all the work, and afterwards 

 take exclusive charge of the young. This is the case 



^0 Yarrell, ' British Fishes,' vol. ii. p. 11. 



31 According to the observ.ations of M. Gerbe; see Giinther's 'Ke- 

 cord of Zoolog. Literature,' 1865, p. 194. 





