PECULIARITIES OF PLA.ICE FROM DIFFERENT FISHING GROUNDS. 327 



in the samples described above from the Norfolk coast, and even from 

 the Brown lUdges. Duncker's male specimens from Heligoland must 

 have been all, or nearly all, immature. It will be seen from my list 

 of Norfolk coast specimens that spinulation often commences on the 

 fin-rays before maturity, and this accounts for the fact that the first 

 stage of the character occurs in a considerable proportion of Duncker's 

 specimens. The smallest in which it occurs is 20'6 cm. long ; the 

 largest in which there is no spinulation at all is 2G"6 cm. long. In my 

 Norfolk coast samples the smallest specimen in which spinulation 

 occurs is 23'5 cm. long, and only one smaller than this was examined, 

 while the largest in which it was absent is 36"5 cm. long. Degree 2 

 occurs in Duncker's specimens, in one specimen 24o cm. long, and one 

 267 cm. long, while in the Norfolk coast specimens the smallest in 

 which this degree occurs is 27"3 cm. long. It is not possible then to 

 conclude from Duncker's specimens whether in the race to which they 

 belong spinulation is much developed or little. There is nothing to 

 contradict the probability that they belong to a race as strongly 

 spinulated in the adult males as the Norfolk coast form or that from 

 beyond the Dogger, and we certainly have no evidence at present that 

 they are less spinulated than those of the Brown Ridges. Duncker 

 unfortunately overlooked the question of ■ the age and maturity of his 

 samples, 



Duncker divides the height of the body into only two degrees, and 

 combines it in his formulai with the length of the head, and I can 

 therefore only attempt to make a comparison from his descriptive 

 remarks. He says that the height exceeds 38 per cent, in the 

 Heligoland plaice but seldom, and it would seem from this that these 

 plaice are rather narrower than those from the Norfolk coast of the 

 same size, and perhaps than those of the Brown Ridges ; but the 

 comparison, under the circumstances, is not worth much. Seventy-two 

 per cent, of the Heligoland specimens have a length of head over 

 24 per cent., and this would seem to show that these plaice were much 

 longer in the head than any of my North Sea samples. But with 

 regard to both these characters it must be remembered that the pro- 

 portion of smaller specimens is much higher than in my samples, even 

 when I consider only those of my specimens which are below the 

 maxima sizes of Duncker's; and I conclude, therefore, that the head 

 is much longer in the younger specimens. Indeed Duncker himself 

 mentions the fact, stating that the 21 smaller females from Heligoland 

 have a mean head-length of 24"9 per cent., and the 24 larger, above 

 23'G cm. in length, a mean of only 23'7 per cent. 



No comparison then is possible except in the characters which do 

 not vary with age, namely, the numbers of fin-rays and gill rakers ; 



