854 



Part III. — Ttventletlt Anmud Report 



A similar comparison may be made between the average size of the 

 females and males of each group, and the particulars are shown in the 

 following Table: — 



I. toll. 



1901. 

 30th May . 

 6th, 7th June 

 31st July . 

 18th October i 

 6th November 



II. to III. 



? 

 94-1 



99- 



96- 



III. to IV. 



2 



91-4 

 95'8 

 91 -.5 

 119-1 

 97-5 



IV. to V. 



79-0 |[lll-2] 



V. to VI. 



VI. to VII. 



6 : 2 



49-1 



94-1 



59-4 



117-6 



100-4 



87-5 



f.4-3 



[56-3] [51 -2] [84 -3] - 



84-1 61-0 



59-4 49-1 



VIII. to X. 



47-9 [35-0] (72-1) 



The observations made above apply also here, and the figures most 

 nearly representing the yearly increase in the females and the males 

 are those of 6th November, but the yearly increment of growth from 

 Series II. to Series III. in the haul must be reduced a few millimetres, 

 as stated above. It will be noticed that the increments of growth, 

 particularly in the males, diminish in each generation after the fourth 

 group, that is to say, about the time sexvial maturity is reached. I'he 

 curve (PI. XIV.) shows that, with the plaice, the males grow as rapidly, 

 or almost as rapidly, as the females until this period is reached, and that 

 thereafter they lag very mu.ch behind the females. The increment of 

 72-1 mm. in the last column, it should be said, is based upon only two 

 females, and no doubt represents rather the growth between the eighth 

 and the tenth generations. 



The differences between the averages of the groups in the Moray 

 Firth hauls, showing the apparent annual increments of growth, are 

 as follows : — 



Females. 



The increments here also show considerable diversity in the different 

 cases, but the means have a certain uniformity of relation, and show, as 

 in the average for Aberdeen Bay, a diminution with age. The apparent 

 increase in length in the two cases in a year may be contrasted as 

 follows r- 



