602 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 Raffaele 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, 1t passes through a larval form denonmeeae 
Leptocephaius brevirostris.” What length of time the develop- 
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Fie, 363.—Larva of Common Eel, Leptocephalus brevirostris of Kaup. (After Kaup.) 
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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 
(“ Kel-Fares”) are already one year old. Some individuals 
apparently spend their whole life in fresh waters, but they are 
barren.t A specimen was kept in confinement in the family of 
the French naturalist Desmarest for upwards of 40 years, growing 
to a length of 45 feet, being already of large size at the time of 
' The biology of the Eel embraces an enormous 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, Rep. 
Fish. Board Scotl. xiii. 3, 1895, p. 192;+G. B. Grassi, Proc. R. Soc. 1x. 1896, 
p. 260, and Mon. Zool. Ital. viii. 1897, p. 233; C. H. Eigenmann, Z’rans. Amer. 
Mier, 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. 
