Fig. I. Lepiocephatus brevirosiris Kaiip (from fig. 15, pi. XVIII, 

 Kaup, Catalogue of the Apodal Fish in the British Museum, 1856). 

 The first drawing in existence of the larval form of the eel, published 

 in 1856 before it was known that the specimen figured was in any 

 way connected with the eel. 



- 147 - 



namely, that the Leptoccphali arc undeveloped forms, the larvae of other fish. He sup- 

 posed however, that they belonged to the ribbon-fishes (Töcwözi/ß^ with the genera 6e/>ö/a 

 and Tyichinrus etc.) and other elongated forms. 



The theory brought forward 

 by Cards regarding the origin of 

 the Leptoccphali raised consider- 

 able discussion amongst naturalists, 

 some opposing it others partly re- 

 cognising its correctness. To the 

 former belonged, for example, the 

 German W. Peters ' who at a mee- 

 ting of the Prussian Scientific Aca- 

 demy in 1868 brought forward a 



young specimen of the ribbon-fish Cepola rubescens 006 m. long from the Mediterranean 

 and showed that it was quite different from the Leptocephali. 



But even before that, in 1864, the American Th. Gill^ had expressed his belief in it, 

 in so far as he declared that the Leptocephali were only the young of other fishes, but not 

 of the ribbon-fishes as Carus had thought. On the other hand Gill expressed the view 

 for the first time, that the Leptocephali were the larvae of eels ("congers"). He thus 

 says 3, "I am almost certain that the typical Leptocephali at least are the young of 

 Congers, and that Leptocephahis Morrisii is the young of Conger vulgaris." 



Later investigations as will be seen have shown that Gill was quite right in his view 

 that the Leptocephali are the young of eels. Gill however has not published the material on 

 which he based his conclusions. These appear quite casually as a preliminary notice in 

 a treatise on other subjects in which he promises a more detailed report. This has never 

 appeared however, though the suggestion which Gill gave to future naturalists has been 

 the basis for our present knowledge of the peculiar developmental history of the eels. 

 Both Gill and Carus deserve to be specially remembered in this section of the history 

 of science for the leading ideas, which later scientists who have been able to advance 

 still further owe to these investigators. 



The first so far as I know who has dealt with the question in detail, that any given 

 Leptocef>/iahis-s^ecies was identical with a species of eel, was the French zoologist Camille 

 Dareste. Without being aware of Gill's note of 1864 Dareste subjected the so-called 

 Leptocephahis Spalansanii (united with L. Morrisii as one species by Kaup and Yarrell) 

 to a close examination and comparison with the common congev {Conger vulgaris). The 

 result was that so many points of resemblance were found between the two forms (e. g. 

 form and position of the nostrils, snout, pectorals, brain, hyoid bone and temporal region), 



1 W. Peters, Bemerkungen über die von Einigen angenommene Verwandlung von Lepiocephalus in Cepola 

 (Monatsber. d. Königl. Preuss. Akad. d. Wissensch. zu Berlin, 1868; Berlin, 1869, p. 130 — 131). 



2 Theodore Gill, On the affinities of several doubtful British Fishes (Proceedings of the Academy of 

 Natural Sciences of Philadelphia, 1864, p. 207 — io8). 



3 Concerning a second leptocephalid form Hyoprorus messinensis Köll. Gill further states (1. c. p. 208) : 

 "The Hyoprorus messinensis appears likewise to be merely the larval form of the Congroid Nettasioma me- 

 lanura. The resemblance between those two forms will be readily appreciated by reference to Dr. Kaup's 

 figures of the two." 



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