EELS. 117 



Owing to the fact that the generative organs of the Common 

 Eel do not ripen in fresh Vater, numerous erroneous impressions 

 have arisen concerning the mode of propagation of the fish, which 

 have only recently been dispelled. It is now definitely established 

 that when five or six years old the Eels migrate to the sea to breed, 

 and they do not return to fresh water. The males have been 

 observed to precede the females, from which they may be dis- 

 tinguished by the sharper form of the snout ; in fact, what in 

 England are called the Sharp-nosed Eel and the Broad-nosed Eel 

 are but the immature males and females of the same species of 

 fish. 



On their way to the breeding place, a zone of the Atlantic off 

 the West of Ireland and France where the water is about five or 

 six hundred fathoms deep, the skin of the fish becomes silvery 

 and bright, the eyes large and dark, and the reproductive organs 

 become fully developed. The Eels spawn at the great depth above 

 mentioned, in the middle of winter, and the innumerable young 

 hatched from the eggs grow to a length of nearly three inches, as 

 the flat, transparent "Leptocephali." 



These larvae (fig. 58 A, p. 118) have perfectly clear, ribbon-like 

 bodies, transparent as glass, and free from colour excepting the 

 eyes, which are black, and are alone visible when the little fish is 

 observed in a jar of clear sea-water. They are called Leptocephali 

 on account of the small size of their ]head. The generic name 

 " Leptocephalus " was applied to the Eel-larvse before their history 

 was known, and it is now merely used to distinguish a stage in the 

 life history of various species of Anguilla, Conger, Congromurana, 

 and other "Eels." Thus, Leptocephalus brevirostris is the larval 

 form of the Common Eel, Anguilla vulgaris ; Leptocephalus 

 morrisii that of the Conger Eel, Conger vulgaris, and so on. 



The Leptocephalus developes from the egg and grows to about 

 three inches in length, and then ceases to feed, and takes no food 

 again until the metamorphosis is complete and the little fish has 

 become an " Elver" (see fig. 58 D). 



As the metamorphosis of the Leptocephalus into the Elver 

 proceeds, the temporary teeth in the upper jaw are shed, and the 

 pointed snout becomes rounded. The height of the body becomes 

 reduced, first in the anterior and posterior parts, later in the middle 



