GRA YLING—SMEL T— SHAD— EEL 



36. 



Shad. 



EeL 



Of the herring family (Clwpeidce) two species live in fresh water, 

 of which, the allis shad (Clwpea alosa), is found along the coast of the 

 North Atlantic, whence it enters the rivers for the purpose of spawning. It 

 is bluish above and silvery underneath ; and when young has a black blotch behind 

 the numerous slender gill-rakers. The twait-shad (0. finta) is a similar fish, but 

 with a more slender body, and stout bony gill-rakers, from twenty-one to twenty- 

 seven in number, or about one-third as many as those of the preceding species. 



The last group of fresh-water bony fish of central Europe is 

 formed by the members of the eel family (Mura n idee), all of which are 

 characterised by the elongated, round, or ribbon-shaped body, always flattened at the 

 tail-end, and either scaleless or with rudimentary scales embedded in the skin ; the 

 pelvic fins being absent, and the dorsal and ventral fins placed some distance from 

 the head and extending to the tip of or right round the tail. The common eel 

 (A Hi/ a ilia v idgaris), 

 which is variously 

 coloured, ranges in 

 length from 20 to (30 

 inches, and weighs 

 up to 22 lbs. There 

 is considerable varia- 

 bility with regard to 

 the sharpness of the 

 snout, which has 

 given rise to the idea 

 of the existence of 

 several species. Eels 

 occur in all rivers and 

 their communicating 

 lakes discharging in- 

 to the North Atlantic 

 Ocean, as well as 



those flowing into the Mediterranean, but are unknown in the streams flowing into 

 the Black Sea, and are therefore absent from the Danube. They are provided with 

 small gill-slits, which can be closed so as to enable them to remain some time out 

 of water. They are tenacious of life, bite hard, and feed on water-insects, and 

 occasionally on plants. 



For more than half a century naturalists have been acquainted with a small 

 pellucid marine creature, elongate in shape, and much flattened from side to side, 

 with a disproportionately small head. Such specimens of these fishes as were 

 taken in the early days of its history were captured near the surface, in company 

 with jelly fishes and other transparent creatures ; and it was not long before it 

 became evident that t here were several kinds of these leptoceph alids (Leptoceph alvs), 

 as, from their ridiculously small heads, they were named. One of these lepto- 

 cephalids living in an aquarium at Roscotf, Brittany, gradually became opaque and 

 cylindrical, till finally it assumed the appearance of a minute conger-eel : and in 

 1901 it was demonstrated that a leptocephalid living in swarms in deep water near 



