58 Modern Fishculture in Fresh and Salt Water. 



The same may be said of the brook trout ; but trout 

 breeders learn to separate the sexes at other seasons by 

 their general appearance without being able to describe 

 exactly how. An old male trout is readily determined 

 by its lank sides and general air of a dilapidated roue, 

 but a vigorous male of three years old before putting 

 on his autumnal dress is very like the female, and is 

 only to be distinguished by a trained eye, and even then 

 mistakes occur. It is a matter of doubt if the yearlings 

 can be separated by sexes with anything approximating 

 a certainty. The males of a northern sea fish closely 

 related to t^e smelt, and known as the capelin, Mallotus 

 villosus, are said to be provided "with a ridge of closely- 

 set, brush-like scales, by the aid of which two males, one 

 on each side, hold the female, while she runs with great 

 swiftness on the sandy beach and there deposits her 

 spawn," a clear case of polyandry, which is exceptional 

 among fishes, which vary more in their methods of re- 

 production than the members of any other class. The 

 well-known hooked lower jaw of the male Atlantic sal- 

 mon, Salnw salar, is only a nuptial appendage, which 

 is afterward absorbed ; but in several of the Pacific 

 species of salmon this is a permanent mark of the male, 

 and from this feature they have received from Profes- 

 sors Gill and Jordan the generic name of Oncorhyn- 

 chus, and have been removed, in their revision of the 

 Salmonidce, from the genus Salmo. To this genus be- 

 long the so-called "California salmon," now O choui- 

 cha of the new nomenclature, and four other species. 



Among the strikingly formed and brilliantly colored 

 tropical fishes there are often marked differences in 

 the sexes, both in structure and color, and one known 

 as the gemmeous dragonet, CalUonynions lyra, has been 

 described by Linnajus, and several subsequent natural- 



