FISHES. 147 



Anal fin moderate or rather long. Ventral fins nearly median in position. Pectoral 

 fins inserted low. Lateral lines present. Outline of belly rounded. 



The stomach in all the Salmonidas is siphonal, and at the j)ylorus are many (1.5 to 

 200) comparatively large pyloric coeca. The air-bladder is large. The eggs are 

 usually much larger than in fishes generally, and the ovaries are without special duct, 

 the ova falling into the cavity of the abdomen before exclusion. The large size of the 

 eggs, their lack of adhesiveness, and the readiness by which they may be imjiregnated, 

 render the Salmonidaj jieculiarly adapted for artificial culture. 



The SalmonidoB are peculiar to the North Temperate and Arctic regions, and with- 

 in this range they are almost equally abundant everywhere where suitable waters 

 occur. Some of the sjiecies, especially the larger ones, are marine and anadromous, 

 living and growing in the sea, and ascending fresh waters to spawn. Still others live 

 in running brooks, entering lakes or the sea when occasion serves, l)ut not habitually 

 doing so. Still others are lake fishes, ajiproaching the shore, or entering brooks in the 

 S]iawning season, at other times retiring to waters of considerable depth. Some of 

 them are active, ^•oracious, and gamey, while others are comparatively defenceless, and 

 will not take the hook. They are divisible into eight readily recognizable genera, — 

 Coi-ef/onus, T'lecofflossus, Unichi/mi/sfax, Stenodus, Thi/7nalli/.<:, Onrorhtjuchus, Salmo, 

 and SalveUmcs. These groups may be discussed in order. 



The genus Coregonus, which includes the various species known in America as 

 lake white-fish, is distinguish.able in general by the small size of its mouth, the weak- 

 ness of its teeth, and the large size of its scales. The teeth, especially, are either 

 reduced to very slight asperities, or else are altogether wanting. The sj)ecies reach a 

 length of one to two feet or more. With scarcely an exception they inhabit clear 

 lakes, and rarely enter streams except to spawn. In far northern regions they often 

 descend to the sea, but in the latitude of the United States this is rarely possible for 

 them, as they are unable to endure impurities in the water. They seldom take the 

 hook, and r.arely feed on other fishes. From their restriction to the waters of the dif- 

 ferent lake systems in which they live, numerous local varieties have come about both 

 in Europe and America, distinguished by characters less constant and less inij)ortant 

 than those which separate the different species. European writers have somewhat 

 inconsistently regarded these v.arying and intangibly different forms as distinct sjiecies, 

 and many of them have come to the conclusion that almost every lake system of Scan- 

 dinavia, Scotland, and Russia has several species which are peculiar to it. Dr. Gun- 

 ther observes that " the sjiecies of this genus are not less ninnerous than those of 

 iSalnw, some having a very extended geographical range, whilst others are confincrl to 

 very limited localities. They are less subject to variation than the trout, and there- 

 fore more easily characterized and distinguished. Hence we find that naturalists who 

 look with distrust on the different species of Salmo are quite ready to admit those of 

 Corecjonusr In my experience, the variableness in Coregonus has been underesti- 

 mated, and the American species at least are all fishes of wide range, varying consider- 

 ably with their surroundings. None of the other species reach the size, or have the 

 value as food, of our common white-fish. 



The species differ considerably in the form and size of the mouth, in the form of 

 the body, and in the development of the gill-r.akors. These differences have led to the 

 est.ablishment of about five sections, or subgenera, the extremes of which differ remark- 

 ably, but which gradually ])ass from one into another. Of the species, the following 

 are among the most noteworthy. Coregonus oxyrhynchus, the Schnapel of Holland 



