B&port on the. Distribution of the Larvcc of the Heel. 7 



southern half receives a poi-tion of its stock, at any rate, from 

 the North of Scotland. The absence of records of glass-eels in the 

 southern North Sea fi-om November to February may be due to the 

 lack of observations during these months. For, as stated by 

 Schmidt, Gilson obtained large numbers off Oape Griz Nez in the 

 beginning of Febiniary. We cannot judlge too accurately the time 

 of arrival of the glass-eel off the coast from the time of the ascent of 

 the elvers of the neighbouring streams ; for, as we see from the 

 Scottivsh records, the glass-eels may be off the coast as early as 

 December, although the ascent of the rivers is not apparently under- 

 taken much before the month of May. The records for the winter 

 months in the southern North Sea are very incomplete. There are 

 Danish records, however, for the months of March and April, and 

 from these it is obvious that part of the stock is at least derived 

 from the north. Johansen has given February as the date of the 

 earliest record for the " Sound," whilst the pelagic glass-eels occur 

 in quantities in the Salter paris of the Danish waters in the months 

 of March and April. Thus these records are in good agreement 

 with the times of arrival of the glass-eels off the Scottish coast, and 

 confirm the view that the Baltic derives part of its stock of eels by 

 way of Scottish waters. The Norwegian record of a glass-eel taken 

 in April in the northern part ol the North Sea might possibly be 

 that of an individual which had entered the North Sea early by waj^ 

 of the North of Scotland, and had been carried by the anti-cyclonic 

 current round the North Sea. 



Our records for »Scotland are too few, and belong to too many 

 different year groups, to make any comparison as to the relative sizes 

 of the Leptocephali and glass-eels with those from other localities ; 

 but the reduction in size during the metamorphosis is brought out 

 in the table. 



The annexed chart illustrates, in a summary way, the points 

 already set forth. We see the Leptocephali distributed in the 

 month of August from westward of the Hebrides to the north of 

 Shetland, in the line of the Gulf-stream current. Obsei^ation in 

 the same region being lacking for the months of September and 

 October, we lose track of the migration during that period. But we 

 next pick up the young- glass-eels in the month of November, just 

 within the North Sea, to the eastward of the Pentland Firth and the 

 Fair Isle Channel. In the middle of the North Sea, all the records 

 relate to the months from December to February. On the other 

 hand, the whole of the observations in the eastern part of the North 

 Sea, eastward of 2° E., including all those in the region of the 

 Skagerak and on the Norwegian coast, are for the months of March 

 and April. The same is true of the observations within the Firth of 

 Forth, and much the same is indicated also by those in the Moray 

 Firth. The net result, accordingly, is that the Leptocephali, in 

 their pa.ssage round the North of Scotland, are metamorphosing into 

 glass-eels in the autumn months ; that a great stream of them is 

 passing through the northern North Sea about December and there- 

 •after till February ; while from this central stream the glass-eels 

 spread coastwards, on either side of the North Sea, reaching the 

 coast about March and April. They then ascend the rivers as 

 " elvers," in May or during the latter part of April, especially during 

 the first half of May. 



