tECULIAKITIES OF PLAICE FROM DIFFERENT FISHING GROUNDS. 319 



111 my results in the majority of cases an approximation to this 

 condition is visible; but I have not calculated the actual mean, or 

 attempted to determine the probable error or mean error of the 

 deviations. The question I have proposed to investigate is merely 

 whether there are between the samples differences in the characters 

 examined, which are sullicient to be definitely demonstrated by 

 comparing the frequencies with which the variations occur. 



The most frequent height of body in the plaice of Brown Ridges 

 is 39, both in the males and females. In the females from 

 the Norfolk coast it is the same, while in the males it is 38. But 

 we cannot say therefore that the Norfolk males are narrower, 

 for among the Brown Eidges specimens there are 16 having a 

 body-height less than 38 per cent., and among the Norfolk coast 

 males only 10. On the contrary, the number of specimens 

 having heights of 4Q, 41, and 42, is greater in the Norfolk coast 

 males than in those of the Brown Ridges, and this does not 

 appear to be due to a difference of age or stage of growth. 

 Duncker found that a considerable decrease in breadth took place 

 between 15 cm. and 20 cm. in length, and an increase 

 after 30 cm. But where two local races are known to differ 

 in absolute size, like those "\ve are now comparing, the question is 

 whether we are comparing samples of corresponding stages and ages. 

 Now there are rather more specimens between 20 cm. and 25 cm. 

 in the Norfolk coast sample than in the other, and therefore more 

 young specimens, and these should be rather narrower than the 

 old specimens ; but we have no reason to suppose that the largest 

 specimens in the Norfolk coast sample are older than those from 

 the Brown Ridges. On the whole, then, we must conclude that 

 the male plaice from the Norfolk coast are broader than those from 

 the Brown Ridges. The single male at 45 was only 20*7 cm. 

 long. The females of the Norfolk coast are also slightly broader 

 than those from the Brown Ridges. 



It will be seen that the difference between the sexes in height 

 of body is very slight, but what superiority there is, is on the side of 

 the females, and this is in agreement with Duncker's results. 



In the Plymouth females the body-height 38 per cent, is the 

 most frequent, while the males appear to be broader, the maxi- 

 mum being at 39. On the other hand, in the plaice from north 

 of the Dogger Bank, although there is no maximum frequency, 

 the number of individuals being small, the much greater breadth 

 of body is suOiciently obvious. A comparison of the lists of 

 specimens from, the Norfolk coast, and from the more northern ground 

 which 1 have given, will show that the greater breadth of the more 



