194 ON THE GROWTH OF 
mined in March, when they had spawned and were 
about to return to the sea, scarcely any were to be 
seen. My observations, however, are too limited to 
warrant the deduction of any general conclusions in 
relation to this curious subject, which certainly merits 
further investigation. 
Researches relative to the growth of the Salmon 
and also to the economy and growth of the Sewin, or 
Bull-trout, conducted on the foregoing plan, have 
been continued as suitable occasions presented them- 
selves ; and I am induced to insist upon the decided 
advantage which a recourse to physiological pheno- 
mena possesses in investigations of this kind over the 
customary practice of mechanically marking fish as 
objects of experiment, in consequence of the various 
sources of error to which the latter mode of proceed- 
ing is exposed. 
Persons, in their endeavours to determine the rate 
of growth in fish by marking specimens, too fre- 
quently employ subordinate agents to carry their in- 
tentions into effect, to whom not only their system 
of marks is of necessity made known, but the antici- 
pated result is also communicated. Now, should it 
so happen that the agents are dependent upon their 
employers, or in any respect interested in making the 
event appear to coincide with their preconceived 
opinions, the desired object may be easily attained 
either by secretly marking specimens of a larger size 
than those which they were instructed and perhaps 
