42 DR. J. MURIE ON IRREGULARITY (Jan. 13, 
waters because no suitable floods occur for them to come down; 
and hence they are obliged to stay an extra year in fresh water. 
It may be that these fancy Parr-markings are a provision of nature 
for concealment when in the young state. 
«There is good evidence of a second migration of Smolts in the 
month of September. This is quite a new fact; but Mr. Buckland 
is fully inclined to believe it, because he is of opinion that as yet no 
universal law can be defined as respects migration of Salmon. 
“« Nature seems to anticipate the deaths of a large number during 
their migratory ascent and descent, so that a Salmon river, like 
Jacob’s ladder, has fish most months of the year, some going up and 
others going down. If nature sent all the Smolts of the first year 
into the sea in the spring of the second year, some accident might 
happen and all be destroyed. 
«Tt happens instead that the crop of full-grown Salmon becomes 
due about the fifth year from those reared in the first year; thus 
a certain number are always coming into condition. 
« As respects the return of Grilse, these are equivalent or pro rata 
to the descent of the Smolts. It is not at all a likely circumstance, 
from what is known of the return numbers, that the large quantities 
which as Smolts arrive in the sea in the spring of the second year 
will ascend in July and August of the same year. But there can 
be no question that they sometimes do so, if Sir William Jardine’s 
remarks on Salmonidee be consulted. 
“ Furthermore, it is a curious circumstance that in 1867 no Grilse 
came back from the sea throughout the entire United Kingdom. 
Concerning this fact a consultation was held at Mr. Buckland’s 
rooms, and among those present were several experienced Scottish 
netters. The opinions expressed were very diverse, and may be 
arranged numerically thus :— 
«1, Some held that the fish had never been hatched. 
«2. Some concluded they never went down. 
«3. Others believed the fish were all destroyed in the sea. 
«4, Others conceived that the deficiency of return Grilse was 
caused by an unusual natural phenomenon unknown to man, yet 
wide-spread. 
«5, Several parties expressed themselves that the fish would re- 
turn early in the summer and autumn of 1869; and, strange to say, 
they did come back in enormous numbers at the time specified. 
Indeed the Irish fisheries in 1869 have far surpassed most of the 
previous seasons, and particularly in the vast preponderance of Grilse 
compared with Salmon. Some of the Grilse were large; but the 
majority were not much, if any, larger than their ordinary dimen- 
sions. 
“In estimating the value of a Salmon-fishery, the calculation 
ought to be based upon an epoch of five years, or a quinquennial 
period. A generation of men is counted by thirty years; so in like 
manner a generation of Salmon ought to be estimated at five years. 
Some say, however, nine years ; but the law of probability is rather 
in favour of five years. 
