274 How to obtain it. 



now finding out many things about the genus Salmo that were 

 unknown and unthought of a few short years ago. 



It is well known that trout in their natural haunts assume 

 endless varieties ; indeed it would be difficult in most cases to 

 find two exactly alike. We find in a great many instances races 

 of yellow, silvery and dark-coloured trout (often called black trout) 

 inhabiting the same lake. In some streams which are frequented 

 by marine or anadromous forms we often find a considerable 

 variety, and every connecting link may be obtained at times 

 between sea-going and fresh-water forms, as for instance, Salmo 

 trutta and Salmo fario. In certain cases undoubtedly these fish 

 have crossed with each other, and it may be their descendants 

 have crossed again, thus producing considerable variations, quite 

 enough to puzzle the older naturalists who were not fish culturists, 

 and therefore had not the same facilities for ascertaining the real 

 truth. When we come to deal with these fish in a practical 

 manner, within the inclosed boundaries of a fish farm, we find out 

 that there is in reality very little, if any, difference between the 

 races, beyond the inherited greater migratory instinct of the sea- 

 going kinds. They spawn here at the same time and in the same 

 places, and I have more than once found trutta paired withfarw. 

 The mingling of the two races in our streams is inevitable, and 

 knowing what we do now as to the fertility of the offspring there 

 can be no doubt whatever that the two forms do at times get 

 considerably mixed. 



Occasionally, owing perhaps to some exceptional circum- 

 stance, such as rain after dry weather, or it may be a sudden 

 change of temperature, the streams frequented by the spawning 

 fish become crowded, and the involuntary mingling of the two 

 races must, one would think, occasionally take place. I have 

 seen both forms spawning in such close proximity that I am fully 

 convinced that milt and ova of the two races must occasionally 

 come in contact, and impregnation take place. Anyhow, we have 

 the intermediate varieties occurring in Nature and we can bring 

 about exactly the same results by artificial means. 



We know that in the human family some individuals have a 

 much greater propensity for roaming than others, and some races 

 of men exist who make periodical migrations. Why should not 



