FISHES. 



333 



the gemmeous dragonet "from its brilliant gem-like colors." 

 When fresh caught from the sea the body is yellow of various 

 shades, striped and spotted with vivid blue on the head; the 

 dorsal fins are pale brown with dark longitudinal bands; the 

 ventral, caudal, and anal fins being bluish-black. The female, 

 or sordid dragonet, was considered by Linnseus, and by many 

 subsequent naturalists, as a distinct species; it is of a dingy red- 

 dish-brown, with the dorsal fin brown and the other fins white. 



Fig. 30. Xiphophorus Hellerii. Upper figure, male; lower figure, 



female. 



The sexes differ also in the proportional size of the head and 

 mouth, and in the position of the eyes;'^ but the most striking dif- 

 ference 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 con- 

 "finement, 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. "^^ The young 

 males resemble the adult females in structure and color. Through- 

 out the genus Callionymus," 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. 



'2 1 have drawn up this description from Tarrell's 'British Fishes," 

 vol. i. 1836, pp. 261 and 266. 



13 'Nature,' July, 1S73, p. 264. 



" 'Catalogue of Acanth. Fishes in the British Museum,' by Dr. Gun- 

 ther, 1861, pp. 138-151. 



