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data from the places in Spain, France and England, where an elver fishery is carried on. 

 Even if the data from these countiies are not so complete as they will be, and even if 

 there may be some variation in the time of arrival of the elvers in different years, yet 

 there can scarcely be any doubt that the Chart in its present form gives already a fairly 

 correct picture of the true conditions. 



If we now compare this Chart with the Chart, Plate X, which shows the distribution 

 of the earliest known developmental stages of the eel, namely Stage l {Leptocephahis 

 bycvirostris), it appears to me that the solution of the question is at once evident. It 

 cannot be the situation further to the south or north which determines the time of ap- 

 pearance of the elvers, as the ascent at North West Ireland already occurs in December, 

 indeed even in November, that is, just as early as far to the south on the French 

 coast, at Bayonne, whilst on the other hand the ascent at Comacchio in Italy begins only 

 in the beginning of February (at which time it also begins so far north as the east 

 coast of the Hebrides). If we investigate however the distance from the various places out 

 to the deep water, for example lOOO meters curve, Plate XII, along which or outside which 

 the larvae were found, we see immediately that the places (Spain, Bayonne, Ballyshannon) 

 where the ascent already occurs before New Year are those which lie nearest to 

 the deep waters And if we note the conditions on the tract from the Bay of Biscay 

 to the Bristol Channel, which in the nature of the case is the tract from which we obtain 

 the best tested information, we see that where the lOOO meter curve bends away from 

 the coast the ascent of elvers takes place later in the year. In other words, 

 the time of appearance of the elvers on the coasts of Spain, France and Great 

 Britain depends especially on the relative distance of these coasts from 

 the deep water where the spawning of the eel takes place ^. In agreement with this we 

 see that the ascent on the North Spanish coast, where depths of more than 1000 meters 

 occur at less than 15 miles from land, may already begin in September, that is, about 

 the same time of year as I have found the metamorphosing eel- larvae off Scotland. 

 The elvers have thus practically no distance to travel to get to the Spanish coast. 



The conditions are thus quite clear as regards the coasts directly washed by the 

 Atlantic. When we turn to the other parts of North Europe, especially the coasts of 

 the North Sea, we find that we still require many new investigations before the question 

 can be said to be cleared up in all details. This applies especially to the whole of the 

 Scottish and English east coast as also the regions from the north of France, along Belgium, 



1 At Limerick in S, W. Ireland, which lies far up in the mouth of the Shannon, ca. 60 miles from the sea, 

 the elvers are observed often in mild weather already in January, so there is no doubt that they must occur 

 considerably earlier on the coasts outside. The condition at Cadiz in Spain (cf. p. 205) seems to agree with 

 this well. There the elvers are given as appearing in the beginning of December, but the Chart .shows that 

 the distance here from the deep water is but short. The same considerations used here for the Atlantic coasts 

 will assuredly also on closer investigation prove to hold for the Mediterranean. An examination of a 

 depths-chart of the Mediterranean shows amongst other things, that there is a relatively long distance from the 

 deep water to Comacchio, where the elvers according to undoubtedly trustworthy information first begin the 

 ascent in February, 



2 Cf. Vaillant's definite statement that the ascent from the sea ceases at essentially the same time 

 (namely in May) everywhere along the French coast, in spite of the fact that it begins in different months (see 

 p. 198), also the information from the biological station of Santander, Spain, which states that the elvers there 

 ascend in the period from October or September to April or May (see p. 200). 



29* 



