482 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [20] 



(1) For the development of their organs of generation eels need salt 

 water.* As has now been ascertained beyond a doubt, the eels leave 

 the rivers and brackish lakes when their organs of generation have 

 scarcely begun to develop, and enter the sea that these organs may 

 there reach their full development. That this migration to the sea is 

 undertaken for the purpose of spawning is fully proved by the fact that 

 in spring the young eels come from the sea, and this view is further 

 strengthened by the circumstance that when the eels commence to 

 migrate they cease to eat, just like other fish do, during the spawning 

 season. 



(2) The development of the organs of generation takes place in the 

 sea, not near the coast, but farther out in deep water. Considering the 

 immature condition of the eels when they begin to migrate, the develop- 

 ment is exceedingly rapid. In a few (five to six) weeks they reach matur- 

 ity, according to the time when they enter the sea. Near Comacchio 

 the eels migrate from the beginning of October till the end of December. 



(3) The river eels have their settled spawning places in the sea.t 

 These are mud-banks which the eels visit in large numbers for the pur- 

 pose of spawning. The young fry develop on these banks, and go to 

 the mouths of the rivers in the beginning of spring, about eight to ten 

 weeks after their birth. 



(4) The old eels, both males and females, die soon after the spawning 

 season. The extraordinarily rapid development of their organs of gen- 

 eration exhausts them to such a degree that they die soon after having 

 spawned. This is the reason why they are never seen to return.:}: 



It is hoped that this short treatise on the eel question may do its share 

 in giving a new impetus to its scientific investigation and may aid 4n 



*" Some peculiarity in the chemical composition or the organic contents of the water 

 of the Black Sea must be assigned as the reason why there are no eels in the whole 

 territory of the Black Sea nor in the Danube and its tributaries. 



t The Chioggia fishermen have pointed out to me several of these mud-banks in the 

 Adriatic. 



t Siebold was the first to express this opinion (see farther below). An intelligent 

 Chioggia fisherman, owner of a vessel, in answer to my question, what became of the 

 old eels, replied: "They die on the mud-banks after they have made young ones." 

 This view finds its scientifically proved analogy in the lamprey. Panizza in de- 

 scribing the sea lamprey (Petromyzon marinus L.) remarks that both the males and 

 females of this kind of lamprey are invariably found dead after the spawning season. 

 (See Panizza: "Memoria sulla lampreda marina" in the "Memorie dell' Instituto 

 Lombardo di scienze," vol. ii, Milan, 1845, p. 48.) Regarding the river-lamprey 

 (Petromyzon fiuviatiUs L.) Statius Martens, the translator of Linn6's System of Nature, 

 says (vol. iii, 1774, p. 232), that after it has finished spawning it gradually declines 

 and finally dies. Concerning the small lamprey {Petromyzon Planeri, Bloch), the 

 discoverer of its larva (the Ammoccetes branchialis), August Miiller, who had observed 

 the spawning process of this fish in the river Panke near Berlin, says that he had wit- 

 nessed the very same phenomenon. (SeeA. Miiller, "Vorliiufiger Bericht fiber die Entwi- 

 ckelung der Neunaugen" in "J. Miiller's Archiv," 1856, pp. 323, 324.) Theodor von 

 Siebold (in his "Die Susswasserfische Mitteleuropa's," p. 378) says: "A very interest- 

 ing faot, discovered by A. Miiller in the course of his observations, is the complete dia- 





