320 PECULIAKITIES OF PLAICE t"llOM DIFFEEENT FISHING GROUNDS. 



northern specimens does not depend entirely on age or size. A similar 

 great height of body was found by Duncker in the Cattegat plaice, 

 which exceed in this respect the plaice of the Baltic. The latter 

 are stated to be mostly from 38 to 39 per cent, in height, like 

 my specimens from Brown Ridges and the Norfolk coast. Now 

 the largest specimens from the Cattegat examined by Duncker 

 were between 39 and 40 cm. in total length ; but Petersen, 

 in the Report of the Danish Biological Station, 1893, records specimens 

 up to nearly 22 inches, or 55 cm. Thus the Cattegat plaice do 

 not appear to be very much smaller on the whole than those of 

 the northern part of the North Sea, and we may conclude that they 

 are similar to these. Whether they agree with them in other characters 

 will be seen in the course of this paper. 



In the last two columns I have added the figures of Plymouth and 

 Brown Ridges to represent a southern race, and the figures of the other 

 two localities to represent a northern, and it will be seen that though 

 the maximum frequency still remains in both sexes of both races at 

 39, yet the northern race is distinctly broader. 



In the second set of tables are seen the frequencies obtained by 

 taking all individuals regardless of sex, and here also the greater 

 breadth of the Norfolk coast specimens, and of those from north-east 

 of the Dogger Bank, is evident. 



Length of Head. The most conspicuous fact that appears from the 

 figures referring to this character is that in all four cases the females 

 are distinctly longer in the head than the males. This agrees with 

 Duncker's results. Duncker also found that the length of the head 

 decreased during the growth of the fish. Such decrease is evident in 

 my list of the males from the Brown Ridges, where the length 20 

 occurs seven times among the 15 largest specimens, and only greater 

 lengths occur among the 37 smaller. The length 19 per cent, occurs 

 only once, and that is in the largest male from beyond the Dogger 

 Bank. But a sinular decrease is not perceptible in the females. In 

 the Norfolk coast females the length 24 per cent, occurs eight times, 

 twice in the largest specimens, three times in specimens between 30 

 and 40 cm., and three times in specimens between 20 cm. and 30 cm. 

 The greater length of head, then, in the females of the Norfolk coast 

 is not due to a greater proportion of young specimens in this sample. 



In the samples from the Brown Ridges and the Norfolk coast the 

 maximum frequency is in both sexes at 22, but in the case of the 

 Norfolk coast the greater lengths are more frequent, and the shorter 

 less frequent than in the case of the Brown Ridges. It is not, however, 

 so obvious that the specimens from north-east of the Dogger Bank 

 have longer heads than those of the Norfolk coast, or even than those 



