41 S Professor D'Arcy W. Thompson [March 22, 



a circling current flows down our eastern coasts, across to Denmark, 

 and in part out again along the Norwegian shore. The direct 

 influence of this system of currents on the life of fishes is immense, 

 for by its means their floating eggs and young are dispersed and 

 disseminated broadcast. In the south those of the plaice and sole 

 are carried over to their nursery grounds on the flat Danish shore ; 

 and in like manner the eggs and fry of the cod are drifted from the 

 western coasts round the north of Scotland into the North Sea, and 

 in part out again to the Sea of Norway. 



Simply and clearly we may see by our chart the distribution of 

 temperature in the north Atlantic, due on the one hand to the Grulf 

 Stream current, and on the other to the opposing currents from the 

 Pole, that bend westward in their southerly course and cool the New- 

 foundland Banks and the shores of the Eastern States, while a minor 

 offshoot from the direction of Iceland, submerged beneath the warm 

 Atlantic waters, approaches or invades our own seas. We see, in pass- 

 ing, the close pressed isotherms on the Newfoundland Banks, where 

 the two waters meet, and we may note, by the way, that it seems to 

 be a fact that fish tend to accumulate just at such meeting places of 

 different waters. But looking broadly at our own temperature pheno- 

 mena the most striking points are : our western coast bathed by the 

 warm current, the eastern remote from its influence ; again the rapid 

 change of temperature from the favoured regions of southern Ireland 

 and south-western England as we go farther north ; and lastly the 

 uniformity of temperature over the wide region that sweeps round 

 from the North Sea by way of Iceland all round the North Atlantic 

 to Newfoundland again. 



The difference of temperature between our western or southern 

 coasts and the eastern is in close relation with the great contrast 

 between the fish of the two regions. Broadly speaking, to the former 

 belong southern fishes, while fishes whose home and distribution are 

 in the north characterize the latter. There cannot be a more striking 

 contrast than that between one of our fish markets and a market of 

 Lisbon, Genoa or Marseilles. The cod and the haddock, and nearly 

 all their allies (save the hake) are absent from the latter ; flat fish 

 are few, and the great order of the spiny-finned fishes, the bream and 

 the sea perch, the mullet, the gurnard, and a multitude of others, 

 mostly alien to our markets and strange to our eyes, form the staple 

 commodity. A difference, similar in kind though less in degree, 

 exists between our western fisheries and those of the North Sea. The 

 pilchard, the chief Olupeoid of the Atlantic coasts, finds its appro- 

 priate temperature on the Cornish coast, and rarely penetrates the 

 colder waters to the east. The hake, which takes the place of the 

 cod along the Atlantic seaboard, comes round indeed into the North 

 Sea witli the Gulf Stream eddy, but in meagre qaantities. The 

 bream, which both fresh and salted is an important food of the poor 

 on the west of Ireland, is not in the North Sea an article of commerce. 



