OF THE BRITISH ISLANDS. 173 



ascending into perfectly fresh water to deposit their spawn. 

 During their migration to fresh water they are much es- 

 teemed for food. The Severn in the months of April and 

 May is especially famous for its Shad fisheries. 



FAMILY VII EELS (Muranufa). 



Body very elongate, cylindrical or band-shaped, naked, 

 or with rudimentary scales ; gill-opening very small ; vent 

 remote from the head ; no ventral fins ; vertical fins, if 

 present confluent, or separated only by the projecting tip 

 of the tail ; the humeral arch not attached to the skull. 



Their attenuate snake-shaped bodies, absence of ventral 

 fins, and the continuity of the long dorsal and anal fins, distin- 

 guish the members of the Eel tribe 'conspicuously from all 

 other fish. The most familiar British form, the common 

 freshwater or Silver Eel (Anguilla vulgaris), No. 187, in- 

 cludes a large number of local varieties, formerly described 

 as distinct species under the respective titles of the Sharp- 

 nosed, Broad-nosed, Dublin, and Snig Eels. It is a re- 

 markable circumstance that this fish, though capable of 

 breeding in ponds or rivers, repairs, where facilities are 

 afforded it, to salt-water to deposit its spawn, its habits 

 being in this respect the converse of that of the Salmon. The 

 fry, when hatched, ascend the rivers in vast numbers under 

 the form of " Elvers," to the waters from whence their 

 parents migrated. Artificial ladders, formed of hay or straw 

 loosely twisted into bands, are often provided to enable the 

 little Elvers to climb over weirs, and other natural obstruc- 

 tions, that would otherwise intercept their upward progress. 

 The descent of the adult Eels to the spawning-beds likewise 

 takes place in shoals, the period of their migration, which 

 by known signs may be calculated to within a few hours, 



