BREEDING PLACES OF THE EEL SCHMIDT 283 



that only two species of fresh-water eels could be shown to exist in 

 the Atlantic area : A western, Anguilla rostrata, which is met with 

 in the West Indies and northward of there in America and South- 

 west Greenland, and an eastern Anguilla vulgaris, which is dis- 

 tributed throughout Northern and Western Europe, the Mediter- 

 ranean countries, and the islands of the Atlantic from Iceland to the 

 Canaries (figs. 6 and 15). The eels found in the Azores are also 

 Anguilla vulgaris, whereas the eels of Bermuda belong to Anguilla 

 rosfrata. In externals the two species are hardly distinguishable 

 one from another, but certain numerical characters afford a means. 

 The number of vertebrae in particular is a valuable character, An- 

 guilla vulgai^ having on an average about seven and a half more 

 vertebrae than the American eel {ca. 114.7 against ca. 107.2— c/. 

 fig. 1). If we take the trouble of counting the vertebrae it will be 

 only a very few specimens per thousand which can not be referred 

 w ith certainty to the one or the other of the two species. This fact 

 has proved of great importance in the investigations at sea, since it 

 was found that the larvae of the European and of the American eel 

 are mingled together in certain areas of the ocean. 



In spite of the enormous area of the European eel, statistical in- 

 vestigations failed to demonstrate the existence of local races, as has 

 been done with so many other species of fishes. All the samples, 

 from Iceland to Madeira and from Cyprus to the Azores, yielded the 

 same average values for the characters under consideration. 



As will be seen from the following, this is entirely in agreement 

 with the result of our work at sea. 



The investigations made at sea fall naturally into two groups: 

 (1) those carried out from the State-owned steamship Thor, which 

 was equipped for marine research, during the years 1903-1910. These 

 investigations, the general purpose of which was to study the repro- 

 duction and breeding grounds of the principal food fishes, were made 

 in Danish waters, in the North Sea, and in the Norwegian Sea, in 

 the Atlantic off the West Coast of Europe from Iceland to Morocco, 

 and in the Mediterranean. (2) Investigations in the open Atlantic, 

 carried out in 1911-1921, but with a lengthy interruption occasioned 

 by the war. For these we were unable to use the Thor, her radius 

 of action being too small. They were made from numerous Danish 

 vessels on Transatlantic routes, with no equipment for marine re- 

 search, and no experts to assist with the work, but furnished only 

 with a net, and with instructions drawn up by myself. Though 

 naturally of a very casual nature, restricted as they were to the 

 course of the vessel in each particular case, these investigations have 

 nevertheless yielded important results, and hearty thanks are due 



