NORTH SEA INVESTIGATIONS. 135 



be deferred. A few general facts may, however, be mentioned. The 

 movement of floating objects, which Dr. Fulton found to occur in his 

 experiments, is in accordance with the fact previously accepted that 

 there is a current to the southward along the east coast of Britain, 

 and another to the north-east from the English Channel along the 

 Continental coast. The meeting of these two currents would necessarily 

 cause a current across the North Sea, from the east coast of England, 

 in a curve towards the Heligoland Bight. This movement, carrying 

 with it the pelagic eggs and larv?e, is probably a very important factor 

 in the explanation of the abundance of young plaice, soles, turbot, 

 and brill in the Eastern Grounds, and generally along the Dutch and 

 German coasts. The northward movement of Channel water along 

 the Continental coast is also probably, in great measure, the cause 

 of the extension of the range of the anchovy, latchet, and mackerel 

 in that direction. But there are details which require further con- 

 sideration. The anchovy, mackerel, and latchet clearly migrate towards 

 the Dutch and German Coasts only in summer, and we know in a 

 general way that along those coasts the summer temperature of the 

 shallow waters is considerably higher than in the northern and western 

 parts of the North Sea. But in winter the sea temperature along the 

 Continental coast is lower than on the English coast; and although 

 this agrees with the retreat of the migratory fish in winter, we cannot 

 say how it affects the plaice, which appears to migrate very little, 

 except from the shore to deeper water, as it grows larger. Another 

 peculiarity of the water along the Continental coast is its lower salinity, 

 due to the quantity of fresh water poured out by the great Continental 

 rivers, and this may be one of the favourable conditions to which 

 the abundance of plaice, soles, turbot, and brill, especially in their 

 young state, is due. 



A brief discussion of the growth and ages of the fish decribed in 

 the present communication may not be without interest, and is in- 

 evitably suggested by the perusal of the memoir on the fiat-fish of 

 Denmark, recently published by the Danish investigator. Dr. C. G. 

 Joh. Petersen.* According to the observations described in that 

 memoir, it is possible, by measuring large numbers of plaice of all 

 the sizes in existence at the same time of the year, to distinguish the 

 broods of successive years, or, in other words, the fish of ages dift'ering 

 by one year. At certain lengths there are larger numbers of individuals 

 than at intermediate lengths, these lengths being, of course, those of 

 the majority of plaice derived from successive spawning seasons. In 



* Report of the Danish Biological Station, iv. 1893, published 1894. [An abstract of this 

 Report, prepared by Mr. F. B. Stead, will be found on page 213 of the present number of 

 this Journal. — Ed.] 



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