160 BRITISH FRESHWATER FISHES 



Delage, who kept a specimen in an aquarium from 

 February to September and saw the transparent 

 ribbon-shaped larva become more opaque and more 

 cylindrical and change into a little Conger. It was 

 not until 1897 that the form known as Leptocephalus 

 brevirostris was shown by the Italian naturalists, 

 Grassi and Calandruccio, to be the larva of the 

 Common Eel. 



This Leptocephalid is about 3 inches long 

 and has a comparatively deep, strongly compressed, 

 transparent body and a small head ; the snout is 

 pointed and the eye moderately large ; the small 

 mouth is furnished with a few pointed teeth ; the 

 vent is placed far back and the continuous vertical 

 fins are confined to the posterior third of the body. 

 Such larvae (PI. XXII, Fig. i) have been taken in 

 considerable numbers in the Atlantic Ocean to the 

 west of the British Isles over deep water, 500 

 fathoms or more, from May to August, swimming 

 near the surface at night and at some distance below 

 the surface during the day ; the feeding, which has 

 enabled the unknown younger fish to develop into 

 a Leptocephalid, has now ceased and the digestive 

 tract is empty. From September to November the 

 Leptocephalids of the Eel may still be captured in 

 the same place, but the metamorphosis has com- 

 menced, the body is less deep, the larval teeth have 

 disappeared, the snout is more rounded, the eye is 

 smaller, and the dorsal and anal fins have begun to 

 grow forward (PL XXII, Fig. 2). From November 

 onwards the migration towards the coasts and 

 rivers is in progress and the transformation continues 

 (PL XXII, Figs. 3 and 4), accompanied now by a 

 decrease in length as well as in height ; finally, the 



