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



upper jaw, as in Anguilla. The margin of the month is wide, as in 

 Angnilla. The tongue is free, as in Anguilla. On the other hand, 

 the youngest elvers which I have observed, have smaller eyes than 

 Leptocephalus brevirostris, and this need not surprise us since we know 

 that in other species of Mura3noids the diminution of the eyes occurs 

 during the metamorphosis. T,he nostrils are separated from one 

 another, the anterior tubes are relatively at a considerable distance 

 from the tip of the snout and from the rim of the mouth. They are 

 in a position in which they are observed in many other Leptocephali, 

 which are destined to transform themselves into adult forms having 

 the anterior nostrils in nearly the same position as in the Common Eel. 

 The posterior nostrils, on the contrary, are not tube-like, and are in 

 the same position as those occupied in the adult Anguilla. It is worth 

 remarking that in other Leptocephali also the posterior nostrils have 

 already assumed the adult position when the anterior ones are still 

 far removed from it. In L. brevirostris I find a larval dentition, 

 which resembles that of the other Leptocephali. In correspondence 

 with the small size of Leptocephalus brevirostris the number of larval 

 teeth is small. Researches fonnded, firstly, on the enumeration of 

 the myomeres ; secondly, upon the enumeration of the dorsal and 

 ventral arches of the vertebrae of the caudal extremity (hypnrals) ; 

 and, thirdly, upon the enumeration of the posterior spinal ganglia, 

 lead with great certainty to the conclusion that the Leptocephalus 

 brevirostris is the larva of a Muraenoid, the number of whose vertebrae 

 must lie between 112 and 117, most probably 114 or 115. Such a 

 Mursenoid is the Anguilla vulgaris. The Mura3noid indicated cannot 

 be any other of those occurring in the Mediterranean, because they 

 all have a number of vertebras higher than 124.* Counting the 

 myomeres in Leptocephalus brevirostris one finds generally only 105 

 complete, five others incomplete, and all the others in a state of 

 transparency and incomplete formation. These latter are fortunately 

 a,t the posterior extremity, where other criteria come to our assistance, 

 namely, the spinal ganglia and the vertebral arches. To show how I 

 arrive at the number of vertebrae which must be possessed by the 

 adult individual, corresponding to a given Leptocephalus brevirostris, 

 I quote the following example : I assume that three vertebras 

 develop themselves in correspondence to the first four incomplete 

 myomeres, and that 105 must develop themselves in relation to the 

 105 complete myomeres, that is to say, between the fourth and fifth 

 myomeres, between the fifth and sixth, and so on, until we reach the 

 105th vertebra, lying between the 104th and 105th myomeres. I 



* Muroenesox savanna is said to have 109 vertebrae, but it is doubtful whether it 

 really occurs in the Mediterranean. The position of its nostrils and the number 

 of its branchiostegal rays render its association with Leptocephalns brevirostris 

 impossible. 



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