"PERFECT-MOUTHED" FISHES 233 



rivers to spawn, the Eels behave in the opposite way. They are 

 fresh-water dwellers that migrate to the sea for the purpose of 

 propagating their species. For a long time the breeding habits 

 of the eels were shrouded in mystery; for although the eggs or 

 larvae of the fish are never found in fresh water, in the spring the 

 streams and rivers are more or less crowded with perfectly formed 

 young eels about 2 inches in length. Owing, however, to the 

 investigations of several noted naturalists, it was discovered some 

 years ago that eels need salt water for the development of their 

 reproductive organs, and that the mature fishes leave their fresh- 

 water haunts in large companies in the autumn and retire to the 

 depths of the sea (about 200 fathoms) to spawn. 



The eggs are light and buoyant and float up to the surface of the 

 sea, and the larvae when hatched are minute, elongated creatures, 

 transparent as glass. They complete their metamorphosis in the 

 sea, and in the spring great companies of young " elvers," as 

 they are called, from 2 to 4 inches long, perfectly formed but still 

 extremely transparent, ascend the rivers in vast multitudes, 

 detachments occasionally leaving the water to take a short cut 

 across a meadow on their way to an inland lake or stream. 



It is not known exactly how long it takes for a larva to com- 

 plete its metamorphosis, but it is supposed that the young elvers 

 when they migrate to the rivers are from six months to a year 

 old. It is not until they have reached their fifth or sixth year, as 

 a rule, that Eels migrate to the sea to spawn. The males are said 

 to leave the rivers first, the females following shortly afterwards ; 

 after spawning it is believed that the eels usually die, and do not 

 return again to fresh water. 



Only two species of eel are found in British waters the Common 

 Eel (Anguilla vulgaris) and the Conger (Conger vulgaris). The 

 Common Eel is of a dark olive colour along the back, and white or 

 pale yellow on the under surface. The long, snake-like body is 

 slightly flattened at the sides and at the tail end, and the skin is 

 smooth, with rudimentary scales embedded in it. The female 

 eel may measure over 3 feet in length when fully grown, the males 

 being always considerably smaller. 



The Conger Eel is entirely marine, and is easily distinguished 

 from the Common Eel by the larger size of its jaws and eyes. 

 The mouth is very wide, the upper jaw being a little longer than 



