182 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



would now be. The question of error now arises, or 

 rather, it will arise when. an attempt is made to compare 

 these results with similar ones made at some future time. 

 Just how to estimate the statistical errors of the modal 

 lengths and of the measures of dispersion adopted does not 

 seem clear. Probably theoretical frequency distributions 

 will have to be calculated from the rough data, and from 

 these the errors of the modes, and the other values chosen 

 may have to be determined. At any rate, the data 

 obtained have been published in extenso for this reason. 



(3) Distribution and Migration of Plaice on the Fishing 



Grounds. 



(a) Nelson Buoy to Liverpool Bar. 



We may summarise the data relative to the sizes of 

 plaice on this fishing ground as follows : — 



May : 3 % are below 15'2 cms. (6 in.) ; 46 % are 



over 19'1 cms. (7-| in.) ; 50 % are between 



15*2 and 191 cms. 

 June: 9 % are below 17*3 cms. (6} in.); 41 % are 



over 20'6 cms. (8 in.); 50 % are between 



17-3 and 206 cms. 

 July: 12 % are below 18'4 cms. (7J in.); 38 % are 



over 21'4 cms. (8J in.); 50 % are between 



18'4 and 21*4 cms. 

 August: 12 % are below 176 cms. (7 in.); 22 % 



are over 22 cms. (8f in.); 50 % are between 



176 and 22 cms. 

 September: 15 % are below 18 cms. (7 in.); 35 % 



are over 22 cms. (8J in.); 50 % are between 



18 and 22 cms. 

 October: 22 % are below 18'8 cms. (7± in.); 28 % 



are over 25 cms. (9f in.); 50 % are between 



18'8 and 25 cms. 



