142 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



catch from Rock Channel represents the poorest plaice 

 taken in the Lancashire and Welsh district, with the 

 exception of one catch from Menai Straits in March — a 

 10-inch fish from the Rock Channel catch weighed only 

 about 4| ounces. 



k / :1 

 The figure is not the graph of the function 



but each of the curves is a smooth line drawn as near as 

 possible to the points representing the actual average 

 weights. It is not drawn absolutely correctly and is 

 intended to show the relative weights at different places; 

 closer approximations can be made to the weights by 

 calculating from the table of values of the coefficient l\ 

 Really true values are not really obtained either by this 

 process or from a graph on which weights calculated from 

 the formula are plotted, because the " constant " k is not 

 absolutely a constant, but often varies slightly in the same 

 series. If it is calculated for each centimetre group in the 

 same catch it is frequently found that it is greater in 

 relation to the larger fish than the smaller ones. That is, 

 the plaice does not grow equally in all dimensions, and 

 the ratio of length to thickness or average width probably 

 varies with increasing age. 



The values of the coefficient Jc for three of the series 

 are plotted in fig. 20. It will be seen that they form 

 curves with one maximum, which in the case of the two 

 Channels is in July. The curves probably rise to the 

 maximum more steeply than they fall to the minimum, 

 but the number of observations is not great enough to 

 enable us to be quite sure of this. The minimum appears 

 to be in January. About the end of November plaice 

 cease to feed as a rule, and very little is found in their 

 stomachs until the end of January. In the case of the plaice 

 taken in Beaumaris and Red Wharf Bays there appears to 

 be a notable difference in that the condition of the fish is 



