and anal fins being bluish-black. The female, or sordid dragonet, was
considered by Linnaeus, and by many subsequent naturalists, as a
distinct species; it is of a dingy reddish-brown, with the dorsal fin
brown and the other fins white. The sexes differ also in the
proportional size of the head and mouth, and in the position of the
eyes (12. I have drawn up this description from Yarrell s British
Fishes, vol. i. 1836, pp. 261 and 266.); but the most striking
difference is the extraordinary elongation in the male (Fig. 29) of the
dorsal fin. Mr. W. Saville Kent remarks that this singular appendage
appears from my observations of the species in confinement, to be
subservient to the same end as the wattles, crests, and other abnormal
adjuncts of the male in gallinaceous birds, for the purpose of
fascinating their mates. (13. Nature, July 1873, p. 264.) The young
males resemble the adult females in structure and colour. Throughout
the genus Callionymus (14. Catalogue of Acanth. Fishes in the British
Museum, by Dr. Gunther, 1861, pp. 138-151.), the male is generally
much more brightly spotted than the female, and in several species, not
only the dorsal, but the anal fin is much elongated in the males.
The male of the Cottus scorpius, or sea-scorpion, is slenderer and
smaller than the female. There is also a great difference in colour
between them. It is difficult, as Mr. Lloyd (15. Game Birds of
Sweden, etc., 1867, p. 466.) remarks, for any one, who has not seen
this fish during the spawning-season, when its hues are brightest, to
conceive the admixture of brilliant colours with which it, in other
respects so ill-favoured, is at that time adorned. Both sexes of the
Labrus mixtus, although very different in colour, are beautiful; the
male being orange with bright blue stripes, and the female bright red
with some black spots on the back.
[Fig. 30. Xiphophorus Hellerii. Upper figure, male; lower figure,
female.]
In the very distinct family of the Cyprinodontidae inhabitants of the
fresh waters of foreign lands the sexes sometimes differ much in
various characters. In the male of the Mollienesia petenensis (16. With
respect to this and the following species I am indebted to Dr. Gunther
for information: see also his paper on the Fishes of Central America,
in Transact. Zoological Soc. vol. vi. 1868, p. 485.), the dorsal fin
is greatly developed and is marked with a row of large, round,
366