the water, it has been found in water that is quite salt, containing 
from 30 to 34 parts of salt per 1,000, although somewhat greater 
or smaller amounts are quite possible. The eggs and young fry 
will usually be living in water containing less salt than that in 
which the adults stay. 
RACES. 
Fishermen believe that there are different varieties of many of 
our species of fishes, and speak of Quoddy herring, Labrador 
herring, etc. Often distinct differences can be found in fish of the 
same kind, but from different places, one variety being deeper or 
thicker than another, or there being differences in colour or in 
average size. These characters are not very good for exact study, 
as they are apt to change with age or the condition of the fish. It 
is better to take characters that do not change with age, such as 
the number of rays in the fins or the number of parts in the back- 
bone. If constant differences in these are found we may be fairly 
sure that distinct races exist. 
The rate of growth of the plaice varies with the locality, but 
the chief cause of this appears to be the temperature. There are, 
however, other differences. The average number of rays in the 
longest fin (dorsal) is higher in fish from Passamaquoddy bay than 
in those from the gulf of St. Lawrence off Cheticamp, and in those 
from the Bay of Islands, Newfoundland it is still higher. There 
are just as distinct differences in width, although in this case the 
size must be taken into account. Those from the gulf of St. Law- 
rence are the broadest and those from the Bay of Islands the 
narrowest. For example the average width of plaice ten inches 
long would be — gulf of St. Lawrence, three and eleven-sixteenths 
inches; Passamaquoddy bay, three and three-eighths inches; Bay 
of Islands, three and one-eighth inches. 
We have therefore fairly distinct races of plaice at different 
points along the coast, but we do not yet know how they compare 
with each other in quality. 
LENGTH OF LIFE AND RATE OF GROWTH. 
The age of a fish may usually be found by examining the scales 
or the small flat bones from the ears (otoliths), for rings on these 
indicate the seasons through which the individual has passed, just 
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