a Transactions. 
in the sea for the longer period—say from May of one year to 
July of the following year—did not seem to attain a very much 
greater size than those which returned in the shorter period. 
The same peculiarity was noticed in the case of tame trouts kept in 
ponds. Some grow much more rapidly than others. It has been 
found that parr become smolts and go to sea, some of them the 
first year; the great majority, the second year; and some not 
till the third year. This too, was exactly the case among domes- 
ticated trout. It was found necessary at the end of the year to 
take the fish out of the pond and sort them. If this were not © 
done, the big ones would eat the little ones, and at the end of 
two or three years their size would be altogether disproportioned. 
some weighing only two or three ounces, others as many pounds, 
I have known cases of domesticated trout reaching 4 lbs. in two 
years, whereas usually it takes three years for a trout to reach 
1 lb., even when domesticated. A smolt let off in May at Stor- 
montfield returned in July, weighing 3 Ibs. On the other hand, 
a smolt which the Duke of Roxburgh let off on 14th May did not 
return until July of the next year, and it had then attained a 
weight of only 6} lbs., having in fourteen months just doubled 
the weight gained by the other fish in three months. These, and 
many other observations, proved that fish spending a long time 
in the sea did not continue to grow at the same rate as in the first 
few months. There was very little doubt that food supply was 
the great incentive which drove salmon to the sea, They did 
feed, and feed voraciously, in our rivers at times. But sometimes 
they took little food—when spawning, for example; when the 
temperature was very low, and when on migration. It was 
quite possible, for these reasons, to get plenty of salmon with 
nothing in their stomachs; and as their digestion was very 
rapid, even after a good meal, no trace of it might be fonnd 
a few hours afterwards. The idea seemed to exist in many 
minds that the huge bodies of the salmon were developed by a 
very indefinite something which the fish managed somehow or 
other to obtain by a process which they called suction ; and this, 
as a recent writer very aptly remarked, pointed to something like 
microscopic supplies. But there was no doubt the food of the 
salmon in the sea consisted largely of herrings, young and old, 
sand eels, crustacea, &c. They followed the young herring shoals 
closely. In many cases they had been found gorged with young 
herrings ; and I have a report from the Highlands stating that a 
ei, a 
