FISHES. 393 



than the male, and she alone has a marsupial sack and 

 hatches the eggs; so that the female of Solenostoma differs 

 from all other Lophobranchii in this latter respect, and 

 from almost all other fishes, in being more brightly colored 

 than the male. It is improbable that this remarkable 

 double inversion of character in the female should be 

 an accidental c .ncidence. As the males of several fishes, 

 which take exclusive charge of the eggs and young, are 

 more brightly colored than the females, and as here the 

 female Solenostoma takes the same charge and is brighter 

 than the male, it might be argued that the conspicuous colors 

 of that sex which is the more important of the two for the 

 welfare of the offspring, must be in some manner pro- 

 tective. But from the large number of fishes, of which the 

 males are either permanently or periodically brighter than 

 the females, but whose life is not at all more important for 

 the welfare of the species than that of the female, this 

 view can hardly be maintained. When we treat of birds 

 we shall meet Avith analogous cases, where there has been a 

 complete inversion of the usual attributes of the two sexes, 

 and we shall tlien give what appears to be the probable 

 explanation, namely, that the males have selected the more 

 attractive females, instead of the latter having selected, in 

 accordance with the usual rule throughout the animal 

 kingdom, the more attractive males. 



On the whole we may conclude, that with most fishes, in 

 which the sexes differ in color or in other ornamental char- 

 acters, the males originally varied, with their variations 

 transmitted to the same sex, and accumulated through 

 sexual selection by attracting or exciting the females. In 

 many cases, however, such characters have been transferred, 

 either partially or completely, to the females. In otlier 

 cases, again, both sexes have been colored alike for the sake 

 of protection; but in no instance does it appear that the 

 female alone has had her colors or other characters specially 

 modified for this latter purpose. 



The last point which need be noticed is that fishes are 

 known to make various noises, some of which are described 

 as being musical. Dr. Dufosse, who has especially attended 

 to this subject, says tliat the sounds are voluntarily pro- 

 duced in several ways by different fishes; by the friction of 

 the pharyngeal bones by the vibration of certain muscles 

 attached to the swim-bladder, which serves as a resounding 



