COMMON EICL. 



]02r) 



the young li;i\iiiL;\ us usual, couiiiiiraliNcK' larger eyes 

 partly in connexion \vith tiie different environments and 

 habits of the tish, and partly owing to the ahove-nien- 

 tioned retrogressions of development, eoiisideralile varia- 

 tions ajipear in the relati\e dimensions of the e\'es. In 

 young Eels (sumetinies even in specimens 8' ^ dm. long) 



small, short tip. (Jill-rakers and pseudobraachi;e are 

 wiinting. Tile line and pointed pharyngeal teeth, weaker 

 tiian tlu; ja\\-teeth, form dense, velvety cards, two above, 

 of an ovaJ shajx^, on the upper pharyng(!als, and two 

 below, of a more elongated sliajie, on a thin inward 

 expansion of the lower pharyngeals, whicii else resemble 



and in the \ariety known as Idtiroslris, the longitudinal ; branchial ai-ches. The upper half of the gill-openings, 

 diameter of the eyes is about ecptal to the interorbital , which ai'c slit-like or curved forwards in a crescent, 



width or at least ^/j thereof. The eyes are comjjara- 

 tively smallest, as a general rule, in the migrating Eels, 

 usually measuring less than " ,, (sometimes only about 

 43 %) of the interorbital ^vidth. In the last-mentioned 

 specimens the interoi-bit.d width is also hardly less" 

 than the length of the snout, in the former sometimes 

 scarcelj' ^ ^ thereof, though the ])ercentage for this re- 

 lation increases with age. Each nostril in the pos- 

 terior pair lies, in the form of a dermal fissure, set 

 obliipiely or in the longitudinal direction of the snout, 

 just before the up])er anterior corner of each eye; the 

 anterior nostils are situated, in the form of dermal 

 tubes, one on each side of the tip of the snout. The 

 mouth is horizontal, with the tip of the lower jaw more 

 or less prominent — most distinctly in old Eels and in 

 latii'osfrif: — and with the corner situated below the eyes 

 or, especially in lafinistris, somewhat behind the per- 



lies just in fi-ont of, the lower half below the base of 

 each |)ectoral fin, their height l)eing ecpial lo this base 

 and about the same as the interorbital widtii. 



The dorsal tin is of about uniform height, though 

 low in front and very gradually increasing in height 

 behind, the increase being proportioned to the percep- 

 tible decrease in depth shown by the posterior third of 

 the body. The longest rays, which measure about ' „ 

 — ^/s of the greatest depth of the body, thus lie in the 

 hindmost part of the fin, just before it slopes to form, 

 together with the caudal and anal tin, a lanceolate ti[) 

 at the end of the tail. The anal fin is similar to the 

 dorsal, but much shorter, commencing, as we have men- 

 tioned, considerably further back, so that the distance 

 between the dorsal tin and the tip of the snout is about 

 70 — 75 % of that between the anal fin and the .same 

 [joint. In Eels 2' , — 7 dm. long this difference increases. 



pendicular from tiie hind margin thereof. The lips are as a rule, during growth, until the body attains a length 



double, fieshv, and tumid, the outer folds being more 

 or less expanded at the sides, in the upper jaw as though 

 the free luaxillaries of other Teleosts were here replaced 

 by this dermal growth; but the underlips are usually 

 broadest. The length of the upper jaw (of the cleft of 

 the mouth), from the tip of the snout to the hind mar- 

 gin of the buccal corners, measures about 26 — 33 %, 

 that of the lower jaw about 35 — 47 ?6'', of the length 

 of the head, the latter proportion in each case being 

 characteristic of latirosfris. The dentition of the month 

 is partly described above. The most characteristic point 

 in the dentition of our Eel, as opposed to East Indian 

 and Australian forms otherwise very closely resembling 

 it, is the absence in the jaw-cards of the longitudinal, 

 toothless ga|j shown In' the last-mentioned forms, thougii 

 the innermost mw in both jaws, even in the European 

 Eel, is made u]> of smaller teeth, and mav, as a rule, 

 be distinguished more easily than the others. The 

 tongue is fleshy, free, toothless, and elliptical, with a 



of about 4Vo dm., but afterwards diminishes, the length 

 of the head thus being generally less in middle-sized 

 specimens, especially in the migrating Eels, than this 

 difference, in large Eels some\vhat greater than the 

 same. But the individual variations appear to deprive 

 the difference of all systematic significance; nor does 

 it seem to j^ossess any importance as an external sexual 

 character. 



The pectoral fins, when expanded, are o\al, often 

 somewhat pointed, and the middle rays (about the 10th) 

 are the longest. The relative length of these fins ex- 

 pi'esses both a distinct alteration of growth, the \()ung 

 having even relatively shorter pectoral fins than the 

 old, and a difference of sex, the males in general having 

 shorter pectoral tins than the females. In 6 Eels (4 c/' 

 and 2 ?) 23 — 41 em. long the average length of the 

 pectoral fins pi-ii\ed to be 3'r> % of that of the body 

 and N'li % of the distance between the anal fin and 

 the tip of the snout. In 7 Eels (all ?) 45 — 68 cm. 



" AccordiTio: to .Jacoby even grenler. 

 ' According to Kkovek up U' .54 %. 



