108 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



fishing-ground and for each month represented in the 

 statistics. The figures in brackets relate to secondary 

 modes and indicate that the catch was obviously hetero- 

 geneous. The method of determination of the modes is 

 given on p. 11. 



Table " Modal Lengths of Plaice of Age-Groups I 

 and II, 1909" given on p. 180, summarises the results of 

 the age-determinations from inspection of the otoliths. 

 The methods and results will be discussed later. 



The Table " Values of the Length-Weight Coefficient 

 h, 1909" given on p. 179, is an attempt to summarise 

 the data relating to the conditions of nutrition of plaice 

 in the Irish Sea. It was hoped that a more complete 

 series of results would be attained, but in the meantime 

 this Table may be useful for future comparisons. Average 

 weights for the fishes examined are not tabulated in the 

 report : evidently they can be obtained by making use of 

 the coefficients and the length-weight formula. The 

 coefficient k is 



1002 # 

 ZnP 



when g is the weight of all the plaice in each cm. group, 

 n the number of fish in each cm. group, and I the mean 

 length in cms. The results of the Table are discussed 

 further on p. 143. 



The Graphs. 



Just how to graph these series of figures was a matter 

 of some difficulty. Merely to plot the points given in the 

 percentage columns of the Tables of length-frequencies 

 leads to confusion for one does not easily see what are the 

 positions of the modes, and the curves are, in some cases, 

 very " jumpy." Smoothing the curves, as already indi- 

 cated, simplifies them, but not sufficiently to assist in 

 estimating the distribution of the lengths. 



