40 
eels, their study became of much greater interest, but it must be 
confessed, that the older descriptions of the Leptocephali are so 
imperfect ånd unsatisfactory, that a certain determination of the 
species from them is impossible; naturally, any attempt to discuss 
the distribution of the species on such åa basis is still more im- 
possible. It may be said that in addition to a good figure, the 
main thing required in a careful description is the exact number 
of myomeres. Grassi and Calandruccio pointed out that the 
number of myomeres in the Leptocephali corresponds to the number 
of vertebræ in the parent form, This fact I have frequently con- 
firmed and we thus have a means of referring a Leptocephalus to 
its parent species as well as of distinguishing between the different 
Leptocephali, even when in other characters there is apparently no 
difference. | 
Though Delage showed that L. morrisii is the larva of Conger 
vulgaris and- Grassi and Calandruccio, on confirming this, 
added 'that several Leptocephali known from thé Straits of Messina 
under various names are the larvåe of C. mystax and C. balearicus, 
yet, up to the present time, figures and descriptions of tese three 
Leptocephali which would enable us to distinguish them from nearly 
related forms have not been published. I have found it nécessary, 
therefore, to study the question anew from the very beginning in 
the only way possible; namely, by counting the ' vertebræ in. the 
larval and adult forms. In this way I have been able to determine 
the larval stages occurring inside the territory investigated, which 
includes the Mediterranean and the North Atlantic north of- ca. 
20? NL. | ME 
The 'full-grown larvae of the Conger-speciés mentioned differ 
in regard to size. C. balearicus has the largest larva (ca. 20 cm.), 
C. mystax the smallest (ca. 13 cm.), whilst the larva of C: vulgaris 
may attain a length of ca. 16 cm. All three species have long 
ribbon-like bodies with the anus far behind near the beginning of 
the tail, nearest in C. balearicus, furthest away in C. vulgaris 
(see figs. 1—6). ; 
