Metamorphosis of the Common Eel. 261 



dispel in the most important points the great mystery which has 

 hitherto surrounded the reproduction and the development of the Com- 

 mon Eel (Anguilla vulgaris). When I reflect that this mystery has 

 occupied the attention of naturalists since the days of Aristotle, it 

 seems to me that a short extract of my work is perhaps not unworthy 

 to be presented to the Royal Society of London, leaving aside, how- 

 ever, for the present, the morphological part of my results. 



The most salient fact discovered by me is that a fish, which 

 hitherto was known as Leptocephalus brevirostris, is the larva of the 

 Anguilla vulgaris. 



Before giving the proofs of this conclusion I must premise that 

 the other Muraenoids undergo a similar metamorphosis. Thus, I 

 have been able to prove that the Leptocephalus stenops (Bellotti), for 

 the greatest part, and also the Leptocephalus morrisii and punctatus 

 belong to the cycle of evolution of Conger vulgaris ; that the Lepto- 

 cephalus hceclteli, yarrelli, bibroni, gegenbauri, kollikeri, and many 

 others imperfectly described by Facciola, and a part of the above- 

 named Leptocephalus stenops of Bellotti, belong to the cycle of evolu- 

 tion of Congromurcena mystax ; that the Leptocephalus tcenia, in- 

 ornatus, and diaphanus belong to that of Congromurcena balearica 

 that under the name of Leptocephalus kefersteini are confounded the 

 larvae of various species of the genus Ophichthys ; that the Lepto- 

 cephalus longirostris and the Hyoprorus messanensis are the larvae of 

 Nettastoma melanurum, and that the Leptocephalus oxyrhynchus and 

 other new forms are larvae of Saurenchelys cancrivora, and that finally 

 a new little Leptocephalus is the larva of Muroena helena. 



The form known as Tylurus belongs to Oxystoma, of which we 

 unfortunately know nothing more than a figure by Raffinesque. I 

 have not been able to find the Leptocephalus of Myrus vulgaris, of 

 which I have had only a single young individual, in which the trans- 

 formation was already far advanced. Neither have I found the Lepto- 

 cephalus of Chlopsis bicolorj a very rare form, which is related to 

 Murcena and to Murcenichthys. As the result of these observations, 

 the family of the Leptocephalidae has been definitely suppressed by 

 me ; the various forms of that family are, in fact, the normal larvae 

 of the various Mura3noids. 



In regard to the greater part of the above-named species, the con- 

 trol has been threefold, namely : 



Firstly, anatomical. I have compared the various stages in all 

 their structures, and have made the due allowance for the changes 

 brought about by the metamorphosis at the close of larval life. 



Secondly, natural. I have found in nature all the required transi- 

 tional stages. 



Thirdly, experimental. I have followed, step by step, the meta- 

 morphosis in aquariums. 



x 2 



