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THE AMERICAN NATURALIST [Vol. XLII 



coast, and in 1900, 22,608 in Danish waters, excluding fresh 

 water and the smaller areas of salt water. Yet in spite of these 

 extensive fisheries and the wide distribution of the eel along the 

 coasts of the Atlantic and its tributary waters in Europe, abso- 

 lutely nothing has been known of the spawning grounds, or 

 breeding habits of the eels of these more northern waters. Sex- 

 ually mature eels have rarely, if ever, been taken. Dr. Schmidt 

 records the discovery of but a single sexually mature male eel 

 of the silver (migrating) type in shallow waters off the coast of 

 Denmark. Leptocephalus larvae belonging to the common eel 

 (L. brevirostris) have never been taken, until recently, in the 

 Atlantic. The specimen taken by the Challenger Expedition in 

 the North Atlantic and referred by Giinther to this species proves 

 upon reexamination to belong to another species having 140 

 myomeres instead of the 111-118 characteristic of L. brevirostris. 



In 1904 a single example of this latter species was captured by 

 Dr. Schmidt in the tow nets of the Thor west of the Faeroes, 

 and a few months later Dr. Holt, of the Irish Fisheries Bureau, 

 took a second specimen west of Ireland. These captures gave 

 the clue which Dr. Schmidt has most successfully followed. In 

 the next two years Leptocephalus was discovered by Dr. Schmidt 

 in large numbers in m id-summer to the west of the British Isles 

 and France over depths of 1,000 meters. The transition stages 

 between the hyaline pelagic larvae in the Leptocephalus stage 

 and the colorless " elvers " which have long been known along 

 the northern and western coasts of Europe were also found by 

 the Thor but at the close of summer and in the autumn. 

 After a thoroughgoing investigation of these grounds and of the 

 data regarding the movements and distribution of the young 

 elvers along the coasts of Great Britain and continental Europe 

 Dr. Schmidt comes to the following conclusions. 



The common eel of northern Europe spawns in the Atlantic 

 Ocean west of the British Isles and southward at least as far as 

 the northern coast of Spain. The essential features of the 

 spawning ground are (1) a depth of at least 1,000 meters and 

 (2) a temperature at this depth above 7° C. This belt is a 

 relatively narrow one along the edge of the continental shelf 

 as it rises from the Atlantic basin. Leptocephalus larva? have 

 long been known in the Mediterranean and a much greater ex- 

 tension of the spawning grounds beyond the known limits to the 

 south is not improbable. The Atlantic basin with its greater 

 depths and lower temperatures appears to afford an effectual 



