PECULIAUITIES OF PLAICE FROM DIFFERENT FISHING GROUNDS. 339 



rays was a little lower, but in such a small number of specimens the 

 difference does not seem of great importance. 



From Niendorf and Kiel there were 26 males, 30 females ; the length 

 of tlie males was 201 cm. to 38'5 cm., of the females 208 cm. to 

 30G cm. According to Duncker the squamation and coloration are 

 intermediate between the Greifswald and Konigsberg forms. The 

 Niendorf males were narrow, and these were few in number and of 

 large size ; the length of head slightly greater than in the Konigsberg 

 sample, a fact very probably due to the greater proportion of females. 

 The mean of the numbers of dorsal fin-rays was only a little over 56, 

 that of the ventral the same as in the Greifswald sample. 



Duncker's North Sea specimens were collected near Heligoland, 

 therefore in the sea ; at Cuxhaven at the mouth of the Elbe ; and at 

 Hamburg. Considering the migratory habits of the species, it is obvious 

 that these must be considered as belonging to one region, and Duncker 

 admits that they are difiicult to distinguish. The Heligoland specimens 

 are stated to have been obtained in July and August, and it is surprising 

 that flounders should be found abundantly in the sea at that time of 

 the year. But perhaps the fact is explained by the shallowness of the 

 water, and the proximity of the two large rivers Elbe and Weser. We 

 find, however, as might be expected, that the Heligoland specimens are 

 the largest and doubtless the oldest. The numbers and sizes are : — 



'&^ 



Heligoland . . 15 males, 23'0 cm. to 3r5 cm. 



29 females, 23-8 cm. to 421 cm. 

 Cuxhaven . . 18 males, 224 cm. to 28'0 cm. 



7 females, 22*5 cm. to 26*1 cm. 

 Hamburg. . . 14 males, 151 cm. to 27*8 cm. 



13 females, 22-2 cm. to 27-8 cm. 



In these North Sea flounders the rougli tubercles are limited to the 

 bases of the fins and the lateral line, while the scales on the rest of the 

 body are smooth and cycloid ; the tubercles occur chiefly at the anterior 

 part of the lateral line, and in the middle region of the bases of the 

 fins. The number of gill-rakers is on the average two or three higher than 

 in the Baltic (15 to 22). The fin-rays are more numerous. The body is 

 narrower ; but in the length of head no constant difference was evident. 



I cannot altogether agree with Duncker in his views with regard 

 to the comparison between the variations of the plaice and flounder 

 in the North Sea and Baltic. He considers that the two forms approach 

 one another to some extent in the Baltic more than they do in the 

 North Sea. In the two cases we find a similar modification in the 

 greater roughness of the scales, in the greater breadth of the body, and 

 the reduction in the number of fin-rays. The number of gill-rakurs 



