CuAP. XII. Fishes. 335 



like those of the female. As so frequently occurs with secondary 

 sexual characters, both sexes of some species of rays (for instance 

 U. batis), when adult, possess sharp pointed teeth ; and here a 

 character, proper to and primarily gained by the male, appears 

 to have been transmitted to the offspring of both sexes. The 

 teeth are likewise pointed in both sexes of B. maculatu, but only 

 when quite adult ; the males acquiring them at an earlier age 

 than the females. "We shall hereafter meet with analogous 

 cases in certain birds, in which the male acquires the plumage 

 common to both sexes when adult, at a somewhat earlier age than 

 does the female. With other species of rays the males even when 

 old never possess sharp teeth, and consequently the adults of both 

 Sbxes are provided with broad, flat teeth like those of the young, 

 and like those of the mature females of the above-mentioned 

 species.'" As the rays are bold, strong and voracious fish, we 

 may suspect that the males require their sharp teeth for fighting 

 with their rivals ; but as they possess many parts modified and 

 adapted for the prehension of the female, it is possible that their 

 teeth may be used for this purpose. 



In regard to size, M. Carbonuier " maintains that the female of 

 almost all fishes is larger than the male ; and Dr. Giinther does 

 not know of a single instance in which the male is actually 

 larger than the female. With some Cyprinodonts the male is 

 not even half as large. As in many kinds of fishes the males 

 habitually fight together, it is surprising that they have not 

 generally become larger and stronger than the females through 

 the effects of sexual selection. The males suffer from their 

 small size, for according to M. Carbonnier, they are liable to be 

 devoured by the females of their own species when carnivorous, 

 and no doubt by other species. Increased size must be in some 

 manner of more importance to the females, than strength and 

 size are to the malfS for fighting with other males; and this 

 perhaps is to allow of the production of a vast number of ova. 



In many species the male alone is ornamented with bright 

 colours; or these are much brighter in the male than the 

 female. The male, also, is sometimes provided with appendages 

 which appear to be of no more use to him for the ordinary 

 purposes of life, than are the tail feathers to the peacock. I am 

 indebted for most of the following facts to the kindness of Dr. 

 Giinther. There is reason to suspect that many tropical fishes 

 differ sexually in colour and structure; and there are some 

 striking cases with our British fishes. The male Cullionymus lyra 



' '" See YarrcU's account of the cellent figure, and p. 422, 432. 

 rays in his ' Hist, of British l'"ishes.' " As quoted iu 'The Farmer, 



tol. ii. IHJC, ]>. 411), with ^in (a.- 186c', il liaS. 



