THE CALIFORNIAN SALMON. 
115 
a family which, being one of the most recent creation — 
no fossil true Salmo being known — is composed of forms 
not yet specifically differentiated.” 
THE GEOWTH AND DEVELOPMENT OE THE 
SALMONIDJE. 
The salmon, the trout, and sea-trout, in their early 
stages, grow at nearly the same rate for the first year, the 
trout being rather more advanced. In each of the three 
varieties mentioned, however, the rate of growth is most 
unequal in individuals of the same age. If one hundred 
ova of brown trout be taken from the same fish, and 
hatched out at the same time, at twelve months old, some 
of the young trout will have grown to eight inches in 
length, while others will not have reached four inches. 
The same curious difference in the growth of individuals 
has been observed in salmon and salmon trout. 
In no other animal is the difference in the rate of 
growth of specimens of the same age, and subject to the 
same conditions, so marked as in the salmonidae. 
When the alevins of trout or salmon leave the shell, the 
fish is about three-quarters of an inch in length. In about 
three to four weeks, the yolk sac is absorbed, this result 
being hastened by a higher temperature, or retarded by a 
lower one. The young salmon then becomes a parr, and soon 
the parr-marks can be distinguished: and at three months old, 
when about two inches in length, these marks are clearly 
developed. At six months old, the parrs have attained to 
an average length of three inches, some having reached 
four inches ; at nine months old, their length is four to 
five inches ; and at twelve months, some will have reached 
seven to seven and a half inches ; while the bulk of them 
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