6o2 TELEOSTEI chap. 



development takes place, not near the coast, but further out in 

 deep water. As a rule it is not until the fifth or sixth year 

 that the Eels go to the sea for the purpose of propagation, which 

 takes place at great depths — at least 200 fathoms. Males have 

 been observed to precede the females. The breeding season over, 

 the Eels do not return to fresh waters, but are believed to die 

 soon after. The eggs were discovered by Eaffaele in 1888 in 

 the Gulf of Naples, and shortly after Grassi and Calandruccio 

 finally settled the question of the breeding and development of 

 the Fish from observations made in the Mediterranean. Their 

 conclusions are thus summed up : — " The Common Eel matures 

 in the depths of the sea, where it acquires larger eyes than are 

 ever observed in individuals which have not yet migrated to deep 

 water. The abysses of the sea are its spawning places ; its eggs 

 float in the sea water. In developing from the egg, it undergoes 

 a metamorphosis, it passes through a larval form denominated 

 Leptocephalus hrevirostris.'' What length of time the develop- 



FiG. 363. — Larva of Common Eel, Le2}tocephalus hrevirostris of Kaup. (After Kaiip.) 



ment requires is not yet fully established, since the Leptocephali 

 are rarely found at the surface, most of the specimens studied by 

 Grassi and Calandruccio having been obtained from the stomach 

 of the Sun-Fish (Orthagoriscus mola) in the Straits of Messina ; 

 but it is believed that the young Eels or " elvers," which ascend 

 our rivers in such prodigious numbers in spring and summer 

 ("Eel-Fares") are already one year old. Some individuals 

 apparently spend their whole life in fresh waters, but they are 

 barren.i A specimen was kept in confinement in the family of 

 the French naturalist Desmarest for upwards of 40 years, growing 

 to a length of 4^ feet, being already of large size at the time of 



1 The biology of the Eel embraces an enormoiis literature. The following 

 general recent accounts should be consulted :— L. Jacoby, Die Aalfrage (Berlin, 

 1880), translated in Rep. U.S. Fish Comm. 1882, p. 463 ; H. C. Williamson, Sep. 

 Fish. Board Scotl. xiii. 3, 1895, p. 192 ; G. B. Grassi, Proc. E. Soc. 1.x. 1896, 

 p. 260, and Mon. Zopl. Ital. viii. 1897, p. 233 ; C. H. Eigeumann, Trans. Amer. 

 Micr. Soc. -xxiv. 1902, p. 5. For a summary of our knowledge of the larval forms of 

 European species, cf. J. T. Cunningham, Journ. Mar. Biol. Ass. (2) iii. 1895, p. 278. 



