58 
IV. — GROWTH OF THE FLAT FISH. 
Relation of breadth and weight to length. — In the report 
for 1903, p. 40, I gave a chart which showed approximately the 
average relationship of breadth and weight to length in plaice. It 
was found that the breadth when plotted out formed a straight line 
of 30° slope, and it was concluded therefore that the average relation 
of breadth to length was -58 to 1. The weight was shown similarly 
to form a curve of the form, w=kl 3 , or w=k (bl)§* The measure- 
ments made at the trawling experiments, and in connexion with the 
marking of the fish, have furnished the materials for constructing 
similar charts for the dab, flounder, sole, and turbot. (Chart 4.) 
The breadth of the dab when mapped out in relation to the 
length is also approximately a straight line of -55 to 1. The weight 
forms a curve like that given for the plaice, — there is much variation, 
but some of it at least is due to the difficulties in weighing on board 
the steamer. 
The breadth of the flounder is found to bear a relationship to the 
length of -57 to 1, and the weight forms a curve which expresses the 
average relation to length. 
The breadth of the sole approximates to -44 of the length, and 
the weight clearly bears a similar relationship to the length to that 
shown in the preceeding examples. 
The line of breadth of the turbot is interesting because it is more 
clearly a straight one than in the other forms, and is related to the 
length as -77 to 1. The. curve of weight in relation to the length in 
this case has been analysed in the manner described in the paper on 
the plaice referred to above, and although it does not form a straight 
line it is nearly a straight line, so that the weight is approximately 
= kl 8 , where k = -125. 
In all these cases, the measurements and weights, with few 
exceptions, were made on living examples. 
Growth of Plaice. — The average determination of weight in 
relation to length is useful in an attempt to state the rate of growth ; 
and in the report for 1904, I was able by means of the chart already 
published to state approximately the yearly growth in weight of 
plaice. I had not then the time to give in detail ' the figures from 
which the conclusions were drawn, but as a matter of fact they had 
Sue also Chart IX in the paper on the Growth of Carcinus mamas in the report for 1902. 
