THE BREEDING PLACES OF THE EEL ^ 



By JoHS. Schmidt, Ph. D., D, Sc. 



Director, Carlsherg Physiological Laboratory, Copenhagen; Member of the R. 

 Danish Commission for the Exploration of the Sea 



[With 7 plates] 



The problem of the propagation and breeding places of the com- 

 mon or fresh-water eel is one of great antiquity; from the days of 

 Aristotle naturalists have occupied themselves therewith, and in cer- 

 tain regions of Europe it has exercised popular imagination to a 

 remarkable degree. It is only during the last three decades, how- 

 ever, that any real results have been attained. 



It has long been known that the full-grown eels move down in 

 the autumn from their rivers and lakes to the sea ; the most impor- 

 tant eel fisheries, indeed, are based upon this seaward migration. 

 The eels do not return again from the sea, but in early spring there 

 appear on the coasts myriads of small young eels, eagerly seeking 

 their way up to fresli water. These eel fry are known in most 

 countries of Europe, and occur in some parts in such quantities as 

 to form the object of a particular industry; for instance, in the 

 River Severn in England, where they are known as ''elvers." Len- 

 til 1896, the elver stage was the earliest stage of development in 

 which the eel was known on the shores of Europe, and it was gen- 

 erally supposed that the elvers arriving in the spring were the off- 

 spring of the eels which had migrated during the previous autumn. 

 They are not, however, altogether minute, like the newly hatched 

 larva of a cod or herring; on the contrary, they are no less than 6-7 

 cm. in length. 



We know then that the old eels vanish from our ken into the sea, 

 and that the sea sends us in return innumerable hosts of elvers. 

 But whither have they wandered, these old eels, and whence have 



1 Reprinted by permission from rhilosopliical Transactions of the Royal Society of 

 London, Ser. B, vol. 211, pp. 179-208. The present paper, however, is not an exact 

 copy of the one published in the I'hilosophical Transactions. In addition to the post- 

 script, which is new, various additions have l)een made, as, for instance, the inclusion 

 of further data from the material collected on the cruises of the two Dattas in 1920- 

 1922. The work on this material is still not completed. Also, 10 figures have been 

 added which do not appear in the paper in Philosophical Transactions, viz, text Figures 

 S, 13, 14, 15, and Plates 1, 2, 7, as well as text Figures 6, 7, and Plate 6, Figure 1. 

 Tlie first seven of these are original ; the last three (text Figures 6, 7, and Plate 6, 

 Figure 1) have been previously published in other papers of mine. 



279 



