142 SALMON AND TROUT. 
to the temperature of the water and forwardness of the 
‘spring. 
The actual bursting of the young salmon from the egg, which 
I have often watched, takes place thus: The fish lies in the 
shell coiled round in the form of a hoop; and the greatest 
strain being at the back, it is at this point that the shell splits 
across. After a few struggles, it is completely thrown off with 
a jerk—leaving the red yolk of the egg, by which the fish is 
nourished during the first five or six weeks of its existence, 
suspended in a conical bag under the stomach. At this ‘ bag 
stage’ of its development the future monarch of the stream is 
represented by a mere ragged line, fringed at the edges and 
almost transparent, the head and eyes being prominent and 
altogether out of proportion to the body, which measures only 
about five-eighths of an inch in length, and is of a pale peach- 
blossom or azure tint. In thirty-five or forty days after hatching 
the yolk bag disappears, and the fry becomes a perfect little 
fish of about an inch long with the fins separated and properly 
developed, and the tail deeply forked at the end. The general 
colour now also changes to a light brown ; and the sides are 
indistinctly crossed by nine or ten transverse dusky bars, or 
parr marks, characteristic of all the species of salmon and trout 
when in an immature state, and which in the true salmon 
remain more or less visible even in a smolt or parr six inches 
long. 
The differences in appearance between the fry of the salmon, 
bull trout and sea trout, and probably also between the fry of 
the other allied species of the genus, are so trifling as to be 
scarcely perceptible, and are, moreover, liable to variations 
with local circumstances. 
The young salmon fry are unable to move about very freely, 
owing to the presence of the vitelline, or yolk bag, which im- 
pedes their motions in swimming, and obliges them when at 
rest to lie perpetually on their backs, unless artificially sup- 
ported. This support they seek to obtain by placing themselves 
amongst gravel or in crevices between stones, exhibiting generally 
