268 Prof. G. B. Grassi. The Reproduction and 



confounded with the pigment round the posterior extremity of the 

 brain, which latter is already present in the preceding stage. In 

 specimens taken at the mouths of rivers this more or less superficial 

 pigment was, so far as I could ascertain, always present. 



As the pigmentation develops itself, the little eel gradually under- 

 goes a diminution in all its dimensions. It results from my measure- 

 ments, that the fully pigmented elver has an average length of 

 61 mm., while for the more or less colourless elver the average length 

 is 67 mm. I found pigmented elvers which were reduced in length to 

 51 mm., a size which I never observed in those elvers in which the 

 development of pigment had not taken place. 



The facts which I have stated demonstrate that the eel goes 

 through a metamorphosis, and that Leptocephalus brevirostris is its 

 larva. Some further considerations remain to be given, although I 

 believe that zoologists will not consider the question still an open 

 one after the record of facts given above facts, which anyone may 

 verify by examining the material which is preserved in my hands. 

 Many to whom I have related my discovery of the history of the 

 Common Eel have objected that eels are found almost everywhere, 

 whilst Leptocephalus brevirostris is limited to Messina. In reply, I 

 must say that, first of all, it is not true that Leptocephalus brevirostris 

 is limited to Messina ; secondly, that at Messina there are special 

 currents, which tear up the deep-sea bottom which everywhere else is 

 inaccessible ; thirdly, although it is true that on the coasts of many 

 countries where Anguilla vulgaris is found, no one has ever seen a 

 Leptocephalus brevirostris ; it is also true that in no country, not even 

 in those where eels are abundant, has anyone ever seen an eel of less 

 than 5 cm. in length. Since it has to be admitted that no one knows 

 the eel before it arrives at the length of 5 cm., there is no greater 

 difficulty in supposing that during this unknown period the eel 

 passes through a Leptocephalus stage than in supposing that it does 

 not do so. The critical study of the literature of this subject, and a 

 great many continued observations, have occupied me for many 

 years, and have been undertaken just in those places where young 

 eels are to be found. They enable me, from my own studies, to 

 affirm with assurance that young eels with the definitive adult form 

 do not exist of less than 5 cm. in length. 



From the study of the memoir of Raffaele on pelagic eggs, I have 

 come to the conclusion that the eggs of his undetermined species 

 No. 10, having a diameter of 2'7 mm. and differing from all the 

 others in the absence of oil globules,* must belong to the Anguilla 



* Kenewed researches have convinced me that this egg is that of Anguilla 

 vulgaris. There is, however, another egg belonging to an undetermined Muraenoid 

 which is devoid of oil-drops, and can easily be confused with the true eggs of 

 Anguilla. 



