WHICH HAVE NEVER DESCENDED TO THE SEA. 467 



I may now finally remark upon the facts that pure Salmon have been raised from eggs in 

 the ITowietoun fishery, that the young have grown to be parr, smolts, and grilse, and that 

 these have given eggs and the eggs so obtained have been successfully hatched. Many 

 sportsmen and fishermen are now reopening the old question that grilse are not young 

 Salmon *. 



The general bearing of the preceding authorities quoted has been in favour of the evi- 

 dence that Salmon confined in fresh water, and especially within that of limited areas, were 

 incapable of reproducing their kind. On the other hand, the fact obtains that land-locked 

 Salmon, both in Europe and America, certainly reproduce their species in fresh water. 



As touching the question at issue, the Howietoun experiments, then, have shown the 

 possibility of not only rearing parr and smolts, but also obtaining ripe ova and milt from 

 them, without their ever having gone to the sea. Thus it is demonstrated that descent 

 to the sea is not, as has been asserted, a dire physiological necessity. 



I would here further observe that although time will be necessary before a definite 

 reply can be given as to how these young Salmon raised from the eggs of parents which 

 have not gone to the sea will thrive and how large such fish will become in freshwater 

 ponds, still any unbiassed investigator must admit that, so far as they have gone, the 

 experiments made at Howietoun among the Salmonidre are pretty conclusive on the 

 following points : — 



(1) That male parrs and smolts may afford milt competent to fertilize ova, but when 

 from fish of the second season, or up to 32 months old, it is (? always) of insufficient 

 strength for strong and vigorous fry to be raised. 



(2) That female smolts or grilse may give eggs at 32 months of age, but those which 

 are a season older are better capable of producing vigorous fry ; while for the purpose of 

 developing ova a visit to the sea is not a physiological necessity. 



(3) That young male Salmonidae are more matured for breeding-purposes than are 

 young females of the same age. 



(4) That although females under 24 months of age may give ova, such are of 

 little use for breeding-purposes, the embryos not becoming well developed or vigorous, 

 while the young when hatched are frequently malformed. 



(5) That the size of the eggs of Salmonida? varies with the age and condition of the 

 parent; but, as a rule, older fish give larger ova than do younger and smaller ones. 



(6) That among the produce of every female fish there may be found variations in the 

 size of the eggs. 



(7) That from larger ova finer and more rapidly growing fry are produced : conse- 

 quently that, by selection of breeders, races may be improved ; while it is only where 

 segregation is well carried out that such selection is possible. 



* On the table, exhibited at the meeting when this paper was read, was a specimen reared at Howietoun from a 

 Salmon egg, the identity of which with grilse I think was beyond dispute. There were also a parr and a smolt 

 shown from the same hatching, evincing the uutenableness of the assumption that the latter have an additional coat 

 of scales to what obtains in the parr. 



SECOND SERIES. — ZOOLOGY, VOL. II. 70 



