9208 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
end (a,). The net so operates as not to catch any fish 
above and below certain limits of length. Obviously the 
majority of plaice catches made by the 6-inch mesh 
trawl net and nets of wider mesh may be represented 
by this curve. The lower limit is determined by the 
condition that the smaller fish escape through the meshes 
of the net; the upper limit in these catches represents the 
upper limit of length of the population sampled. 
The table on this page, and the chart (Fig. 1) 
represent a catch of this kind, consisting of 3,591 plaice 
caught by the same fisherman and vessel in the Horse 
Channel, off Liverpool, in August, 1910. 
Tyree I. 3,591 plaice from Horse Channel, Mersey 
Estuary, August, 1910; 6-inch trawl-mesh. 
Mean length | Observed Calculated Conctante 
cms. frequency frequency , 
15-5 3 imaginary 
16-5 12 Tie N=3591 
17-5 48 69-66 d=1-80451 
18-5 189 162-32 bg= 10-040874 
19-5 311 268-13 Ms3= 13-3703 
20-5 392 352-83 Ma= 288-51 
21-5 413 404-03 6B: =0-181063 
22-5 41] 416-55 B= 2-85942 
23-5 400 393-84 k= —0-173 
24-5 373 346-74 r= 12-21583 
25-5 270 286-28 b= 24-8491 
26-5 292 220-82 Mg = 7-453844 
27:5 186 161-15 m= 2-761981 
28-5 147 110-99 a,= 18-1308 
29-5 66 70-85 a,=6-7183 
30-5 39 41-83 Yo= 417-9071 
31-5 16 19-42 Mean = 23-30 
32:5 11 9-26 Mode = 22:37 
33-5 4 3°12 
24-5 4 1-34 
35:5 4 0:37 


In this, and other tables the notation is that given by W. Palin 
Elderton (Op. cit.) 
The moments given in the table are unadjusted ‘but the calcula- 
tion was made from adjusted moments. 
