256 



DISCOVERY 



further change. The sexual organs, though not fully 

 matured, have greatly developed, and the eyes have 

 increased to an immense size. 



After the departure of the full-grown eels, the next 

 thing that the observer on shore sees is the arrival 

 from the sea of the young transparent glassy elvers, 

 or young eels, of about 2f in. in length. The earliest 

 arrivals reach the rivers of the west coast of Ireland 

 and the north coast of Spain in November and 

 December. Thej' appear in the Loire in January, 

 in the Seine in February, and do not reach the Danish 

 coast till April. 



The passage of the elvers up some of our larger 

 rivers has often been described. They pass up in 

 a steady, continuous stream, heads almost touching 

 taOs, m a broad band, surmounting rapids and faUs 

 ■ and other dangerous obstacles by scrambling up 

 damp rocks or over weirs. 



At Epney-on-Severn, an old-established elver lisherv, 

 organised by a German fishery association in 1908 

 for the purpose of stocking the less favourably situated 

 waters of German^-, and subsequently taken over bv 

 the Ministry of Agriculture and Fisheries, serves as 

 a distributing centre for supplying elvers to lakes and 

 rivers of the British Isles whose natural supplv is 

 deficient. At this fishery the runs of elvers occur 

 at the flood of the spring tides of April and May, 

 the fishing being done chiefly at night by means of 

 a hand net. 



Many elvers remain for a considerable time in salt 

 water, lurking under stones on the shore, before start- 

 ing their journey inland. By about April the elvers 

 become pigmented and opaque, whether they have 

 ascended a river or are still in the sea, and feeding 

 and consequent growth, which had ceased during the 

 last ten months of their larval life, are again resumed. 

 After the capture of the Leptocephalid larvse m the 

 Atlantic in 1904, as mentioned above. Dr. Schmidt 

 began a systematic search for others which, he argued, 

 must be present in immense numbers if only he could 

 find the right locality. \\'orking southwards from 

 off the Hebrides in June 1905, along the edge of the 

 deep water of the Atlantic, he found the larva; in 

 increasing numbers till they reached a maximum 

 off the south-west coast of Ireland, over a depth of 

 about 500 fathoms. These specimens measured from 

 60 to 88 mm., with an average size of 75 mm,, or 3 in., 

 and were similar to, but slightly larger than, those 

 wliich had been found in the Mediterranean — thin 

 transparent lanceolate creatures, with small heads and 

 mouths, well furnished with fine teeth. 



Still seekmg for the younger stages. Dr. Schmidt 

 pushed his researches farther out into the Atlantic. 

 Mainly with the aid of collections made by himself 

 in the schooners Margarethe and Dana, and with over 



500 gatherings made for him on board the ships of 

 various Danish shipping companies, he has traced 

 the Leptocephali westwards and southwards back 

 across the Atlantic, finding them ever smaller in size, 

 but more numerous and spread o\-er a smaller area. 

 In mid-Atlantic, in June, the Leptocephali had an 

 average length of 52 mm., or about 2 in., and still 

 farther to the westward, also in June, a third group 

 was encountered which had an average length of 

 I in. The smallest sizes were found to be concentrated 

 in a comparatively small area, stretching from 22° N. 

 to 30' N. and from 48° W. to 65° W. ^^'ithin this 

 area, and nowhere else in the North Atlantic, larv;e 

 of r- in. or less were found in considerable numbers. 

 Here at last, about 2.500 miles from the mouth of 

 the English Channel, and 500 miles north-east of the 

 Leeward Islands, was the breeding place of the eel. 

 Here (to quote the summary which Dr. Schmidt gi^•es 

 in his paper) " spawning takes place in earlv spring, 

 lasting well on to summer. The tiny larvae, 7 to 

 15 mm., float in water layers about 200 to 300 m. 

 (no to 160 fathoms) from the surface in a tempera- 

 ture of about 20° C. The larvfe grow rapidly, and 

 in the first summer average about 25 mm. They 

 now move up into the upper layers, the great 

 majority being found between 25 and 50 m. (14 to 28 

 fathoms), or at times even at the surface. During the 

 first summer they are to be found west of 50° W. 

 By the second summer they have attained an average 

 length of 50 to 55 mm., and the bulk are now in the 

 central Atlantic. By the third summer they have 

 arri\-ed off the coastal banks of Europe, averaging 

 75 mm., but retaining the compressed leaf-like form. 

 In autumn and winter they undergo a retrograde 

 change which brings them to the shape of 3"oung eels." 

 From the time the}' reach the fully developed larval 

 form in June till the pigmented elver stage is reached 

 nearly a year later, the young eels apparently take no 

 food ; at any rate none has been found in the stomach 

 or gut, and the energy for the journey from the 

 Atlantic to fresh water is derived from its reduction 

 in size. 



But the mystery of the eel was not \et fuUy cleared 

 up. There is an American eel (Anguilla rostrata) 

 which, but for the fortunate chance that it has a 

 smaller number of vertebrre, from 105 to in, could 

 hardly be distinguished from the European species, 

 which has from in to 119. The larval forms can be 

 separated in the same way, since the myomeres or 

 muscle segments, which can be counted in the lar\'0e, 

 correspond in number to the vertebrte. In the 

 western part of the breeding area of the European 

 eel the earliest larval stages of the American eel were 

 found in considerable numbers, both species being 

 sometimes taken in the same net. The question then 



