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Example : Table V, June, 1908-1913. 



The plaice have been grouped into one cm. classes, 13 to 

 14, 14 to 15, and so on : Col. (1) gives the middle points of these 

 class-ranges ; Col. (2) gives the actual numbers of fish measured 

 and belonging to each class-range, and Col. (3) gives these 

 frequencies expressed as numbers per 1,000. Thus all the 

 series given in this report can be graphed on the same scale, 

 and the graphs can be superposed for comparison. Rut the 

 actually-observed frequencies are necessary whenever we 

 require to find the " probable errors," so they must be stated. 

 Col. (4), " S/Voo" gives the results of the process of sunnna- 

 tion : thus the entry, 17-6, opposite the length, 28-5 cms., is 

 the sum, 4-8 + 7-4 + 2-7 + 1-6 + M, of the frequencies 

 opposite 17-6 and below the latter. In this case the summation 

 begins at the bottom of the colunni, but it might as well 

 begin at the top. The entries in Col. (4) are to be read in this 



