THE EEL FAMILY 193 



on the other hand, is spongy as in other fishes, and the milt 

 escapes by a tube or duct. 



Eggs of the buoyant transparent kind found in the Bay of 

 Naples have been recognised as belonging pretty certainly to 

 fishes of the eel family, but have not been connected with par- 

 ticular species. Only the conger and the fresh water eel occur 

 in the British Isles, and no buoyant eggs which could possibly 

 belong to them have yet been found off the British coasts. The 

 ripe eggs have never been obtained from the fish themselves. 

 The young forms have -recently been recognised in certain 

 peculiar, band-shaped, transparent fish previously described as 

 distinct species under the name Leptocephali. It is practically 

 certain that both eel and conger spawn only once and then 

 die, and the males are much smaller when mature than the 

 females. 



The Leptocephali (which means literally small- heads) have 

 some of the characters of the larvae of other fishes, but they have 

 also many striking peculiarities of their own. Like other fish 

 larvae they are transparent and have no scales or silvery layer in 

 the skin, and the bony skeleton is not developed. 



Their chief peculiarities are the great height of the body from 

 the back to the belly and its remarkable thinness from side to 

 side, the small size of the head, and the large size of the whole 

 creature. The largest specimen described was 10 inches long, 

 but the more usual length is 5 or 6 inches, and some are smaller 

 than this. The vent is usually near to the hinder end of the 

 body. It is remarkable that the great vertical depth belongs to 

 the body itself, and is not due to the presence of a broad fin 

 membrane like that of other fish larvae. On the contrary, the 

 fin membrane is very narrow or absent, and in cases where a 

 longitudinal fin with rudimentary rays is present, this also is 

 narrow. In the thin specimens there is no red blood, but speci- 

 mens have been described in which the body was more rounded 

 and red blood was present ; in these the whole development was 

 obviously more advanced. 



These curious forms have been taken on the English coasts, 

 in the Mediterranean, especially in the Straits of Messina, and 

 in the surface waters of the ocean in various parts of the world 

 within the tropics. They are nowhere common except in the 

 Straits of Messina, where they are caught by boys when bathing. 



O 



