THE COMMON OR FRESHWATER EEL 97 



further demonstrated by a similar analysis of the Viviparous 

 Blenny [Zoarces viviparus) a fish not unlike the Eel in form and 

 in habits, but viviparous and therefore not likely to wander 

 much ; it was found that there were great differences in the 

 number of vertebrae in Zoarces populations from different areas. 



So far only full-grown or nearly full-grown eel larvae (60 to 

 90 mm, long) were known, and in 1909 Schmidt could say only 

 that it was probable that the breeding grounds of the Eel were 

 situated out in the ocean far from the coasts. In 19 10 he found 

 two small larvae, 41 and 53 mm. long, in the collection of the 

 Copenhagen Museum, the smaller taken near Madeira, the larger 

 in 30° N., 32° W. In the same year Dr. Hjort, in the Michael 

 Sars, captured 21 larvae of 41 to 60 mm. south and west of the 

 Azores. Schmidt now perceived that the only way to find 

 the breeding grounds of the Eel was to make a survey of the 

 distribution and density of the various sizes of the larvae, and 

 on this work he has been engaged ever since. Good work was 

 done by various Danish vessels sailing to the West Indies, which 

 made occasional short hauls with a pelagic net ; but the most 

 important results were obtained in voyages across the Atlantic 

 made by Schmidt in specially equipped vessels, in 191 3 the 

 Margrethe, which was, unfortunately, wrecked in the West 

 Indies, and since the war the Dana. Thousands of larvae of 

 the Common Eel have been obtained, of all sizes from 5 mm, 

 to 90 mm. long, the smallest still having a remnant of the 

 yolk-sac, and by taking into consideration the size, and the date 

 and place of capture of these larvae, Schmidt has been able to 

 demonstrate the position of the breeding grounds and the 

 history of the larvae from the time it hatches until it becomes 

 an elver. 



On the accompanying chart (Fig. 2) the continuous curved 

 lines show the limits of occurrence of the larvae ; that marked 

 10 embraces an area between about 22° and 30° N. and 48° and 

 65° W. ; this area must include the breeding places of the Eel, 

 for within it larvae less than 10 mm. long have been captured in 

 large numbers, but never outside it. The other curves have 

 been numbered in the same way, i.e. larvae less than 25 mm, 

 in length have been found only inside the 25 curve, etc., and 

 they show how the growing larvae move northwards and east- 

 wards across the Atlantic. It will be seen that on the chart are 

 some curved dotted lines, indicating the size and distribution 

 of the larvae of the American Eel [A. chrysypa or rostrata), a 

 species which differs from the European Eel mainly in the fewer 

 vertebrae (104 to 1 1 1 instead of 1 1 1 to 119), a character which 

 was used by Schmidt to distinguish the larvae, the myomeres 

 being counted. It had always been supposed that the breeding 

 area of the European Eel, wherever it might be, would be 

 7 



