274 MALACOPTERYGII. MUR^NAD^. 



tinuous all round the tail. The dorsal commences 

 at a considerable distance behind the insertion of 

 the pectorals. The gill-opening is a small slit on 

 each side, situated just at the base of the pectoral. 

 The upper jaw is shorter than the lower ; the 

 mouth is furnished with small teeth in each jaw, 

 and a few at the front part of the vomer. The 

 whole body is covered with a thick, smooth skin, 

 well supplied with a slimy mucous secretion. The 

 intestine is long but straight ; the air-bladder is 

 also long, and furnished near its middle with a 

 peculiar gland. A curious pulsating sac has been 

 recently discovered in the tail of the Eels, with 

 regular beats, quite independent of the action of 

 the heart ; the object of this organ is the circu- 

 lation of lymph, a thin colourless fluid, having 

 much of the nature of blood, deprived of its 

 colouring disks. Similar organs have been ob- 

 served to exist in some Reptiles, particularly 

 Amphibia. 



The Eels are properly fresh-water fishes, which 

 migrate to the sea after they have deposited their 

 spawn in the rivers. We have three or four 

 species, differing a little in the form of the head, 

 but sufficiently alike both in appearance and 

 habits to allow of one being taken as a fair sam- 

 ple of the rest. The most common is the Sharp- 

 nosed Eel {Anguilla acutirostris, Yarr.), which 

 is abundant in most of our rivers, lakes, and 

 marshes, as in those of continental Europe. In 

 the waters of high mountains, however, and in 

 countries subject to severe winter's cold, the Eel 

 is not found, as it cannot endure a very low 

 temperature. ** During intense frosts, accom- 

 panied by a piercing east wind, thousands of 



