1144 



THE NATIONAL GEOGRAPHIC MAGAZINE 



LARVAIv KEIvS IN THi: NORTH ATLANTIC 



Larval eels have been collected all the 

 way across the North Atlantic, from 25° 

 to 45° north latitude. i\Iuch new ma- 

 terial of a very interesting character was 

 obtained in 19 10 by Sir John Murray 

 and Dr. Johan Hjort during their notable 

 cruise in the Norwegian government 

 steamer Michael Sars. The larval eels, 

 or leptoccphali, as they are scientifically 

 known, frequent the surface waters, and 

 may be caught in large, fine-meshed tow 

 nets. They possess very feeble swimmmg 

 powers, and it is evident that their move- 

 ments are controlled largely by tides and 

 currents. The smallest specimens are 

 found in mid-ocean south of the Azores, 

 which is the spawning ground for the 

 European eel and probably also for the 

 American eel. It is not easy to under- 

 stand how the x\merican eel, in the 

 course of its metamorphosis, reaches the 

 shores of the United States and Canada, 

 but it is clear that the Gulf Stream car- 

 ries the European species to the coasts 

 of western Europe. As the coasts of the 

 continents are approached, the larvae av- 

 erage larger and larger ; none are ever 

 found near land that are as small as all 

 of those taken in the Sargasso Sea. 



The leptocephali, or larval eels, ap- 

 proach the shores of Europe in three 

 great bodies, corresponding with the drift 

 currents from the Gulf Stream ; one mass 

 goes to and around the northeast coast of 

 the British Isles, another to the English 

 Channel and Bay of Biscay, another to 

 the region of Gibraltar, and thence into 

 the Mediterranean Sea. 



One of the most surprising of the re- 

 cent discoveries about the eel relates to 

 the Mediterranean. For many years the 

 only knowledge we possessed about the 

 larval shapes of the eel came from that 

 sea. In 1856 a larval fish was described 

 l)y Dr. Kaup from the Strait of Ales- 

 sina, which for many years was the only 

 ])lace in Europe where such fish were 

 found. 



It was forty years later (1895) that 

 the Italian investigators Grassi and Cal- 

 andruccio identified Kaup's fish as the 

 larval form of the common eel. No 

 eggs and no very young stages of the eel 



have, however, been discovered in the 

 Mediterranean; and Dr. Schmidt, the 

 well-known Danish investigator, has re- 

 cently concluded that the common eel 

 does not spawn anywhere in the Med- 

 iterranean, and that the entire stock of 

 eels in that sea comes from the Atlantic. 

 One of the strangest facts about the 

 larval eels is that they take n^ food. 

 Here is a vertebrate animal, emerging 

 from an tgg less than one-twenty-fifth 

 of an inch in diameter, growing to a 

 length of three inches in perhaps a year, 

 buffeted about on the high seas, and 

 drifting over a distance of 1,000 miles or 

 more, and yet during this entire period 

 taking no food whatever, and doubtless 

 incapable of doing so, owing to the un- 

 prepared condition of its digestiveorgans. 

 Similar cases occur in other fishes and 

 among insects and other animals ; but 

 there must be fcA , if any, which afi:*ord 

 a parallel to this. 



KElv SCAI,i:S AND WHAT THEY SHOW 



To laymen and fishermen alike the eel 

 is a scaleless creature ; to them its smooth, 

 slippery skin gives no evidence of the 

 scales of extraordinary development and 

 interest that are well known to the biol- 

 ogist. 



While the scales of an eel are small 

 and inconspicuous compared with those 

 of many other fishes, they may easily be 

 made out, with the unaided eye, by a 

 careful examination of any part of the 

 skin. They may be recognized by their 

 parallel arrangement in small clusters, 

 which in turn are disposed at right angles 

 to one another, so that the entire skin has 

 a minute cross-hatch appearance. 



The scale of the eel has come in for 

 a large amount of study in recent years. 

 This study, like that of fishes' scales in 

 general, has thrown much light on the 

 age, growth, and habits of the eel, and 

 has furnished important data that could 

 not have been obtained in any other way. 



Eel scales are thin, flat, elongate-ellipti- 

 cal bodies, very different in character 

 from those of any other American fish. 

 They consist of a base surmounted by 

 minute, refractive, elliptical elevations, 

 arranged in regular concentric series. 



The scales participate in the growth of 



