1864.] ON PISCICULTURE. 145 



[The female Parr cannot spawn ; but the male Parr possesses, 

 and constantly exercises, the power of vivifying Salmon and 

 Grilse eggs.] 



4. The fry remain one, two, and, in some cases, three years in 

 the rivers as Parr before going down to the sea ; about half tak- 

 ing their departure at one year, nearly all the others at two years, 

 and the remainder (which are exceptional) at three years old. 



5. All young Salmon-fry are marked with bluish bars on their 

 sides until shortly before their migration, up to which period they 

 are Parrs ; they then invariably assume a more or less complete 

 coating of silvery scales and become S molts, — the bars, or Parr- 

 marks, however, being still clearly discernible on rubbino- off the 

 new scales. 



6. The young of all the species here included in the genus 

 Salmo have at some period of their existence these bluish bars • 

 and consequently such marks are not by themselves proofs that 

 fry bearing them are the young of the true Salmon (Sahno salar). 



7. Unless the young fish put on their Smolt- dress in May or 

 early in June, and thereupon go down to the sea, they remain as 

 Parrs another year ; and without Smolt-scales they will not 

 migrate, and cannot exist in salt water. 



8. The length of the Parr at six weeks old is about an inch 

 and a half or two inches ; and the weight of the Smolt before 

 reaching the salt water from one to two ounces. 



9. In at least many cases, Smolts thus migrating to the sea in 

 May and June return as Grilse, sometimes within five, generally 

 within ten weeks, the increase in weight during that period vary- 

 ing from two to ten lbs., the average being from four to six lbs. • and 

 these Grilse spawn about November or December, go back to the 

 sea, and in many cases re-ascend the rivers the next sprino- as 

 Salmon, with a further increase of from four to twelve lbs. Thus a 

 fish hatched in April 1854, and marked as migrating in May 

 1855, was caught as a Salmon of twenty-two lbs. weight in March 

 1856. 



10. It appears certain however that Smolts do not always 

 return during the same year as Grilse, but frequently remain nine 

 or ten months in the sea, returning in the following sprino* as 

 small-sized Salmon. 



[It will thus be seen that the fry of the Salmon are called Parrs 

 until they put on their migratory dress, when they be- 

 VoL. I. K No. 2. 



