DIFFERENCES BETWEEN THE SEXES. 
The two sexes are so much alike that an examination of the 
internal organs is usually necessary in order to find out whether 
the fish in question is male or female. One then finds, on examining 
large numbers of individuals, that the males do not reach so large 
a size as the females, for, although during the first few years of life 
there is not much difference between them in the rate of growth, 
when they become mature, the male grows more slowly than the 
female. 
This is not the only reason for the striking lack of large males, 
since a study of fish of different ages shows that for the first two 
or three years there are more males than females, but that the 
older the fish become the smaller is the relative number of males, 
and usually females alone are found among the oldest fish. In 
the gulf of St. Lawrence, where there are fish of many different 
ages, we found the males more numerous than the females among 
the three-year olds, but for the later years fewer and fewer males, 
until finally after an age of fourteen years was reached there were 
only females and of these all ages up to 24 years with the single 
exception of the age of 21 years. 
In the bay of Fundy no very old fish are found and both sexes 
appear to live equally long, the maximum age being ordinarily 
about eight years,-but the same rule holds as to the young males 
being more numerous and the old males less numerous than the 
females of the same age. For example we found the proportion 
of the former to the latter to be for the two-year olds—38 to 22, 
for the three-year olds—11 to 9, for all the older fish—10 to 14. 
There must surely be a higher death rate among the females in 
early life and among the males later, and this is not influenced by 
the temperature, as similar proportions of the two sexes for the 
various years of life are found both where there is rapid growth 
and early maturity in warm water and also where there is slow 
growth and late maturity in cold water. 
FERTILITY. 
Like most fishes the plaice is extremely fertile and sheds many 
thousands of eggs during the spawning period. The actual number 
of eggs varies greatly, but Fulton found from 30,000 to 60,000 in 
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