18 



in a narrow stripe on the part of the back lying between the postoccipital region 

 and the dorsal fin) lying on both sides of the dorsal fin parallel to one another, 

 just as on the ventral aspect, and iip towards the dorsal fin thej' become more 

 parallel to this. All the scales in this part have almost the same number of 

 annual rings (1 — 2), but are of the same size as the 6-}'ear old scales along the 

 lateral line. These scales are obviously laid down in the 4th and 5th years, when 

 the eel increases very greatly in weight, whilst the growth in length is relatively 

 much less than in the foregoing 2 — 3 years; this means that a great increase in 

 thickuess occurs at this time, resulting in the formation of a naked (scaleless) 

 part along the back. 



The condition thus described holds for the longest part of the eel's body; 

 towards the head and the tail there are smaller and younger scales. In the 8-year 

 old individual described here, wiiich was 65 cm. long, the scales along the lateral 

 line eveu 15 cm. from the end of the tail had 3 — 4 annual rings (at the root of 

 the dorsal fin 2 — 4), and at the end of the tail 2 — 3 rings. On the back anteriorly 

 the scales between the pectorals had 8— 4 annual rings, those on the head between 

 the eyes 2 — 3 annual rings, and extremely small scales with 1 — 2 annual rings 

 were found immediately beliind the auteiior nasal openiugs; 1 — 2-year rings were 

 also found on the »cheeks« of the head. On the other haud, the snout, the labial 

 fold of the upper jaw, the under jaw and all the part between its corners, also 

 the »throat« (the first part of the belly) are scaleless. 



I have not been able to find scales on the pectorals, on the other hånd 

 the dorsal fin is covered with scales almost right out to its free margin; on the 

 proximal part the scales have 2 — 3 annual rings, nearer the edge only 1 ; the 

 scales on the dorsal fin are more irregularly distributed than on the body. 



On the anal fin there are quite few scales (1 — 2 years), whereas on the 

 caudal fin — meaniug thereby the portion of the vertical fin whose rays are 

 attached round the last 3 vertebræ of the vertebral column — there are no scales. 



In specimeus of the same size I am able with a little practice to distin- 

 guish easily the males from the females by examining the scales macroscopically, 

 the scales of the male (with more annual rings) being relatively much broader 

 than those of the female. 



Within the group Anguillinæ (Giinther), which includes the genera Anguilla, 

 Gonger, Congromuræna and Uroeouger, Anguilla is the only one that has scales; 

 these Giinther calls rudimeirtary ; they are certainly feeble, but of so connected 

 and fine a structure that the de^cription is not very applicable. We might perhaps 

 with more right call the scaly covering in its entirety rudimentary, as the scales 

 lie very deep in the skin and are onlj' adnate, not covering one another with 

 overhangiug margins; the very large, uncovered parts of skin between the scales 

 point in the same direction; these are indeed so large that there is often easily 

 rooni for a scale there. 



