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G.—THE REPRODUCTIVE ORGANS. 
Some difficulty will be experienced in determining 
the anatomy of the reproductive organs, on account of the 
fact that sexual maturity does not occur until the Plaice 
has grown to a relatively large size, and that to examine 
the varying relations of the system in a really satisfactory 
manner fishes in various phases of reproductive activity 
must be examined. The ordinary marketable Plaice is as 
a general rule an immature fish. There is some consider- 
able difference in the size and age at which it becomes 
sexually mature in different localities, but it will be suffi- 
cient for our present purpose to say that under 17 inches 
of total body length in the female, and 14 inches in the 
male, the reproductive organs are generally immature. Only 
fishes of those sizes should therefore be dissected for these 
organs, and they are best examined some little time prior to 
the spawning season, that is darmg November to January. 
We may here define several terms used in the follow- 
ing pages. The Plaice is spoken of as “‘ mature ’’ when it 
first begins to produce eggs capable of fertilization, or, in 
the male, functional spermatozoa. It is “ ripe’ when the 
ovary becomes distended with mature ova, that is imme- 
diately before the spawning season. It is “spent” or 
“shotten ”’ when all the ova have been extruded in the 
act of spawning. The same terms with the same signifi- 
cance are applied to the various phases of the male in 
respect to the conditions of the testes. 
Considerable differences in the condition of the repro- 
ductive organs may then be expected in Plaice of different 
sizes or of mature fishes captured at different times in the 
year. In the female fish of about 1} inches long ovaries 
and ovarian eggs are certainly developed, but the organs 
are represented by very minute structures situated in the 
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