134 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
out into a nearly horizontal line. An extension of this method 
of making the curves enables us to arrive at the following 
results (for the period 1912-43 :— 
There were 85 hauls in all, and in these either no plaice 
or some plaice were caught ; 
In 61 out of the 85 hauls more than 50 plaice were 
caught ; | 
In 32 hauls out of 85 more than 100 plaice were caught ; 
In 6 hauls out of 85 more than 500 plaice were caught : 
In 2 hauls out of 85 more than 1,000 plaice were caught. 
Then we can easily find out, from the same curves, what was 
the “ shortest half-range”’ of the plaice caught in each period. 
Thus we can say whether one half of all the hauls gave 0 to 50 
plaice, 0 to 60, 0 to 100, 0 to 150, and so on. These half-ranges 
make a kind of averages, and these averages are tabulated 
in the followmg diagrams :— 
400 
300 
200 
; n - 
Ss 6 ae ee Sa ree oe re eS ele aaa Md 
@ 
Variation in the numbers of el fet <e in the i trawl. 
