CiiAP. XII. FISHES. 15 



males, whilst immature, resembling the mature females ; 

 — and, lastly, from the males, even of those species 

 which at all other times of the year are identical in 

 colour with the females, often acquiring brilliant tints 

 during the spawning-season. We know that the males 

 are ardent in their courtship and sometimes fight despe- 

 rately together. If we may assume that the females 

 have the power of exerting a choice and of selecting the 

 more highly-ornamented males, all the above facts 

 become intelligible through the principle of sexual 

 selection. On the other hand, if the females habi- 

 tually deposited and left their ova to be fertilised by 

 the first male which chanced to approach, this fact 

 would be fatal to the efficiency of sexual selection ; for 

 there could be no choice of a partner. But, as far 

 as is known, the female never willingly spawns except 

 in the close presence of a male, and the male never 

 fertilises the ova except in the close presence of 

 a female. It is obviously difficult to obtain direct 

 evidence with respect to female fishes selecting 

 their partners. An excellent observer,"'' who carefully 

 watched the spawning of minnows {Cyj>rinus phoxinus), 

 remarks that owing to the males, which were ten times 

 as numerous as the females, crowding closely round 

 them, he could " speak only doubtfully on their opera- 

 " tions. When a female came among a number of 

 " males they immediately pursued her ; if she was not 

 '' ready for shedding her spawn, she made a precipitate 

 " retreat ; but if she was ready, ^he came boldly in 

 " among them, and was immediately piessed closely by 

 " a male on each side ; and when they had been in that 

 " situation a short time, were superseded by other two, 

 " who wedged themselves in between them and the 



^^ Loudou's ' Mag. of Nat. UiaV vol. v. 1832, p. 681.^ 



