— 9 



D'ARCY W. THOMPSON 



tlie case of area XXIX, immediately to the southward, but nevertheless its indications 

 are clear and intelligible. In five out of the six years there is a maximum in August, 

 and in each year a minimum appears either in midwinter or late autumn: in 1903 the 

 maximum is earlier than usual, in June. In three or perhaps four years out of the six, 

 there is another and earlier maximum in March or April, coinciding with the maximum 

 which regularly occurs at that season in area XXIX. 



In the Reports published in our first Scottish volume on the Granton and Montrose 

 trawling statistics (which refer to fishing carried on for the most part in area XXIX) it 

 is shown that in both cases Cod showed a double annual maximum, firstly in March or 

 April, and secondly in July; the spring maximum, which was much the higher of the 

 two in the case of the Granton trawlers, is that which we have now found to be 

 characteristic of area XXIX; the summer maximum, which was the higher at Montrose, 

 is that which we find to be on the whole characteristic of the more northern areaXXIlI. 



The curve for Codling in area XXIII (fig. 8) is somewhat irregular for the year 1904, 

 but otherwise shows a very regular wave, which comes to a maximum towards the end 



iflOl 



1902. 



1903 



1904- 



1905 



I90S 



20 



10 



^ 



i 



P=: 



t-A 



^=^; 





^ 



?- 



\Ê 



!? 



-.i 



\l 



-K 



ir- 



^ 



t 



t 



I 



Fig. 8. Codling. Area XXIII. 



of the year about October — December, and falls rapidly to a less clearly defined minimum 

 in spring and early summer. There is an indication of steady increase of Codling in 

 this area during the years 1901 — 1903, the last-named year being the best of the whole 

 series; from 1904 to 1906 the average has remained steady. 



If we compare the results shown for our two first areas, XXIII and XXIX, we see 

 that in both of them Cod and Codling differ from one another in their season of 

 abundance: that in both of them Cod come on the whole to a maximum in Spring and 

 Summer, and in both of them Codling are most plentiful in Winter. A closer comparison 

 will show that in respect of Codling there is little or no diff"erence in period of maximum 

 shown for the two areas, but that in the case of Cod the maximum is earlier in the 

 year by two or three months in area XXIX than in area XXIII. Another difference is 

 also apparent: the curve for area XXIX is very smooth and regular, while in area XXIII 

 we have for four out of the six years more or less clear indications of a double cusp, 

 or double maximum. This is probably an indication of a real tendency to a double 



