SEA-FISHERIES LABORATORY. B11 
data, and the curve plotted from the _ theoretical 
frequencies. The approximate expression for y, given 
by Elderton was employed. The curve is not far from 
being symmetrical, and Type II might have been used, 
but we should then have missed deducing the action of 
the fishing gear from the form of the curve. 
TypE IV. 1,593 plaice from Barrow Channel, June, 
1910; 6-inch trawl-mesh. 

Mean Observed Calculated 
length frequency frequency Constants. 
cms. —— | —_——— 
(x) (y) (7) (y) 
14:5 6 14-45 4-67 N=1593 
15-5 15 15-79 18-74 d=0-394852 
16-5 40 16-81 48-75 fg= 5340012 
17-5 89 Mg=3-T5915 
18-5 177 18-13 132-44 é4== 112-3545 
19-5 203 18-75 187-51 B,=0-0928009 
20-5 315 19-98 280-96 Bg= 3-9400 
21-5 260 20-23 290-83 k=0-045 
22:5 239 20-60 297-35 r= 10-66631 
23:5 130 20-86 295-82 m = 6:333155 
24:5 62 21-25 284-73 v= —2-317109 
25:5 31 21-92 245-79 a= 7:020828 
26:5 9 22-64 190-1 Yo= 240-9106 
27:5 8 24-28 79-282 | Mean=20-89485 
28-5 4 26-39 18-868 | Mode=20-65403 
29:5 2 Origin = 19-369677 
30-5 2 
31-5 31:53 0-435 
32-5 
35:5 1 


Typ VI, that is 
Y =Y(«rx—-a 
Here we have an asymmetrical curve, limited in one 
Hekiree 
direction. The range is from a lower limit (a) to infinity. 
The example is a series of measurements of plaice caught 
in a shrimp trawl net of }-inch mesh. The lower limit a 
is 14:108 —10°139, that is 3°96 centimetres, and this is 
probably the actual lower limit of the plaice present on 
the ground at the time (January), since the mesh of the 
