of the Fishery Board for Scotland. 



357 



size up to a certain period is also clear, as the above averages show, 

 but it would seem the females begin to grow slightly quicker than the 

 males after the third summer. In the fourth summer the same 

 divergence is observed, the average size of the females exceeding the 

 average size of the males, and in the fifth year the disparity is marked 

 {vide PI. XIV.), and it doubtless goes on in increasing ratio in the 

 following generation. The disparity in size is therefore due to inequality 

 of growth after a certain period. The largest male I examined in the 

 course of the investigation measured 483 mm., or 19 inches, and the 

 largest female 743 mm., or 29^ inches. In the paper above leferred to 

 the largest male recorded measured 559 mm., or 22 inches ; but males 

 over 40 cm. are very scarce. 



The divergence in growth is no doubt associated with the attainment 

 of sexual maturity in the male at a smaller size than in the female. 



"With regard to the subsequent series or older generations, it is 

 difficult to define their limits or state their average size, but female plaice 

 which have lived thi'ough five summers have a mean size of between 

 fifteen and sixteen inches. Since growth subsequently is slower, and 

 since they may attain a size of thirty inches, it is obvious that there 

 may be many older generations, and that a plaice of the great size 

 mentioned may have i-eached a considerable age.* 



I have collected the measurements of all large plaice from 470 mm., 

 which were measured in the Dornoch Firth and off Lossiemouth, on 

 3rd and 5th November 1900, and grouped in 'S-cm. groups they are as 

 follows : — 



These have been plotted out, as well as in 3-mm. grouping, and they 

 seem to show a division into nine series (PI. XI Va.), divided as follows . — 

 493 mm., 530 mm., 558 mm., 589 mm., 619 mm., 650 mm., 687 mm., 

 714 mm., and 743 mm. The measurements cannot be exact in such 

 large specimens, and this grouping would make the largest about 

 sixteen years old, the averages being separated by intervals of about 35 

 to 40 mm. Many of these large specimens, I may say, were thin, a 

 condition which I have also observed in extremely large haddocks 

 which frequent the inshore waters. 



The size at which male and female plaice first become reproductive 

 has been investigated by several naturalists, and it is evident that it 



* So far as I am aware, tlie largest plaice recorded was one caught on "^Oth May 190'2' 

 on the inshore fishing grounds, and landed at Grim.sby, It measured 38^ inches, and 

 weighed 28^ \h^.—Flsh Trades Gazette, 24th May 1902. 



