146 The Apodes, or Eel-like Fishes 



destined to mature hereafter and be deposited in other years. 

 It is very hard to understand how young eels could find room 

 in the body of their mother if they were retained until they 

 had gained any considerable size. The eel embryo can live and 

 grow for a long time supported by the little yolk, but, when 

 this is done, it can only obtain food outside of the body of its 

 mother. The following circumstances lead us to believe that 

 the spawning of the eel takes place only in the sea: (i) that the 

 male eel is found only in the sea or brackish water, while female 

 eels yearly undertake a pilgrimage from the inland waters to 

 the sea, a circumstance which has been known since the time 

 of Aristotle, and upon the knowledge of which the principal 

 capture of eels by the use of fixed apparatus is dependent; 

 (2) that the young eels, with the greatest regularity, ascend 

 from the sea into the rivers and lakes.' ' 



All statements in opposition to this theory are untenable, 

 since the young eels never find their way into landlocked ponds 

 in the course of their wanderings, while eels planted in such 

 isolated bodies of water thrive and grow rapidly, but never 

 increase in numbers. Another still more convincing argument 

 is the fact that in lakes which formerly contained many eels, 

 but which, by the erection of impassable weirs, have been cut 

 off from the sea, the supply of eels has diminished, and after a 

 time only scattering individuals, old and of great size, are taken 

 in them. An instance of this sort occurred in Lake Musken- 

 gorf in West Prussia. If an instance of the reproduction of 

 the eel in fresh water could be found, such occurrences as these 

 would be quite inexplicable. 



In the upper stretches of long rivers the migration of the 

 eels begins in April or in May; in their lower stretches and 

 shorter streams, later in the season. In all running waters the 

 eel-fishery depends upon the downward migrations; the eels 

 press up the streams with occasional halts, remaining here and 

 there for short periods, but always make their way above. 

 They appear to make the most progress during dark nights, 

 when the water is troubled and stormy, for at this time they 

 are captured in the greatest numbers. It is probable that after 

 the eels have once returned to the sea and there deposited their 

 spawn, they never can return into fresh water, but remain 



