SALMON. 95 



bones, and there is a single surmaxilla. Most of the fresh-water 

 forms are peculiar to the temperate and arctic regions of the 

 northern hemisphere, but one (Retropinna) occurs in New Zealand ; 

 most of the purely marine forms are from the deep sea. Many 

 species are anadromous in habit, i. e. living in the sea, but entering 

 fresh water to spawn and descending again to the sea afterwards. 



The genus Salmo is one of great interest, not only because of 

 the value of the fishes of the genus for purposes of food and the 

 sport which their capture affords, but because of their plasticity 

 and ready response to altered conditions of life. As a rule the 

 fresh-water forms are brown and the marine forms bright and 

 silvery, and the change from the one colour to the other may, in 

 the migratory forms, be observed in the same individual at 

 different periods of its life. In the non-migratory forms the 

 colours are fairly constant while the fish remains in the same 

 waters, but by transferring to new localities brown forms may 

 become silvery and silvery ones brown. If the colouring of the 

 body be disregarded the British species of Salmo may be counted 

 as three in number : — Salmo solar, the Salmon and its varieties 

 Salmo trutta, including all the Trouts, such as Salmon Trout, Bull 

 Trout, Great Lake Trout, Brook Trout, and Salmo alpinus, 

 including all the Charrs. For fuller details of the varieties the 

 visitor is referred to the series exhibited in Cabinet-case 43, and 

 to the specimens in the Wall-case in the British Collection at the 

 West end of the Bird Gallery. 



The true Salmon, Salmu solar, 276, is confined to the northern Salmon. 

 hemisphere between latitudes 75° and 41° or 43° N. ; it occurs 

 in America and Asia as well as in Europe, and does not exist in 

 the Mediterranean and the rivers flowing into it. In Britain the 

 Salmon comes up from the sea into fresh water usually from 

 September or October to January. The nest or redd is dug in the 

 gravel by the female, and after being fertilised by the male, the 

 eggs are buried. The newly hatched fry, or Alevins (272), 

 become free about 90 days after the eggs are laid ; they grow to 

 4 or 6 inches in length, when they are known as Parr or Pink 

 (273) ; the body is marked by vertical blue bars and large spots 

 and is not silvery. The fish either in the first year, or more 

 .usually in the second year, lose the parr marks, and become Smolts 



