— '5 - 



be given by other methods than the usual one above explained. In many cases it is 

 advisable to employ the so-called smoothed curve: this is obtained by taking, not the 

 single values for each centimetre of length as ordinates, but the sum of a series of 

 adjoining single values, for instance for each 5 cm. This is done for instance compa- 

 ratively, in Fig. 2. By means of such smoothed curves many casual irregularities of 

 the original curve are deleted. Another form by which a series of measurements can 

 be represented, and one which is of especial importance for our purposes, is the summa- 

 tion or integral curve shown in F"ig. 2. In this case, the ordinates corresponding to 

 the single centimetre lengths of the abscissa are not the single values appertaining to 

 each length, but the sums of single values, and give, for each centimetre, the sum of 

 the single figures appertaining to this and to all smaller centimetre lengths. If such a 

 summation curve be drawn, as here, as a percentage curve, it is possible to read from 

 it immediately what percentage of the whole quantity of plaice samples lie above or 

 below a certain length, e, g., for our practical purposes, above or below a certain size- 

 limit, of say 25 cm. 



II. 



1. The amount and composition, by number, length and weight, of the 



quantities of plaice landed by the fishery in the different countries in the 



different months from the different areas of the North Sea. The 



relative quantities of young, undersized plaice in the landings. 



The first condition necessary for a successful solution of the practical plaice question 

 is to know, as exactly as possible, how great are the annual landings of plaice from 

 the North Sea, and their composition according to the different age- and size-classes. 



With regard to the size of the landings, we are, thanks to the improved market 

 and catch statistics of late years, fairly well informed. Thus the quantity of plaice lan- 

 ded in 1908 from first-class fishing vessels amounted to about 48 million kg. in 

 round numbers; distributed among the various countries in the following absolute and 

 percentual figures. 



48,167,478 - = 100.00% 



