172 



\ 



Graphic representation i of the reduction in the total length of the eel larva-; 



I. June 



Stage I {Leptocephabis byevirosiris) 



(Average: 75"2i mm.) 



II. January 



Stage 5 



(Average : 73'5i mm.) 



mm 

 90 



86 

 84 

 82 

 So 



78 

 76 



74 

 72 

 70 

 68 

 66 

 64 

 62 

 60 

 58 

 S6 

 54 

 52 



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In I, III and V each circle represents i specimen, in II 3. Between I and II is an interval of ca. 6 — 7 months; betwei 



I I have included the measurements given under II, as it was of importance to include specimens of 

 Stage 5 taken as early in the year as possible, It might be objected that to compare I (Leptocephali from 

 waters S.W. and W, of the British Isles) with elvers (II) from the Bay of Biscay (Bayonne) was not correct, 

 but it is indeed quite justifiable. There can be no essential error in the comparison of I and II unless the 

 French elvers (II) had been larger in the Leptocephaius stage than our specimens from the British Isles (I), 

 but this was excluded from beforehand as the fish young of the same species and at the same stage of devel- 

 opment are known to be larger further north than further south (just as for example, Leptocephaius breviro- 

 slris in the Mediterranean is a little shorter than in the Atlantic). Further, the Leptocephali I took in the 

 northernmost part of the Bay of Biscay (off Brittany) were just a large as the great majority from the waters 

 S.W. of Ireland. 



As regards the comparison of I, III and IV, this has been made for the reasons: (i) that the eel young, 

 which appear on the Danish (and other North European) coasts and in the North Sea in the spring have the 

 ^ame origin as the Leptocephali I have taken in the Atlantic W. of the British Isles. This, I think, is suffi- 



I 



I 



