45 



TUBEBLADDERED GROUP. 



anal fins are rudimental. As in the last genus, the stomach is capable of great 

 distention, and specimens which had swallowed fish of many times their own 

 weight have been found floating in the Atlantic with this organ dilated to its 

 utmost. In a third type (Nemichthys), from depths between five hundred and two 

 thousand fathoms in the Atlantic, the exceedingly elongate body is band-shaped, 

 with the tail tapering to a point, and the jaws produced into a long slender beak. 



It has been already noticed that in one of the deep-sea eels the 

 gill-openings are confluent into a longitudinal slit on the under 

 surface of the body ; and a very similar condition characterises the second family 

 (Symbranchidce) of eels, only in this case the slit is transverse. A better dis- 

 tinction is, however, afforded by the structure of the upper jaw, the margin of 

 which in the present family is formed entirely by the premaxillse, on the inner 

 side of which lie the maxillse. The paired fins are rudimental, and the vertical 



Single-Silt Eels. 





BENGAL SHORT-TAILED EEL (1 nat. Size). 



ones wanting . while the scales, if present, are minute ; and accessory breathing- 

 organs may be developed. An air-bladder is wanting, the stomach has no blind 

 appendage, and the ovaries are furnished with ducts ; the vent being situated far 

 behind the head. Whereas the majority of these eels inhabit fresh and brackish 

 waters in tropical Asia and America, they are also represented in Australia, where 

 one genus is marine. Of the fresh-water forms, the most remarkable is the 

 amphibious eel (Amphipnous cuckia) of Bengal, in which there is an accessory 

 breathing-apparatus, the body is scaled, and the pectoral girdle is detached from the 

 skull. There are only three gill-arches with rudimentary laminaB, separated from 

 one another by narrow slits ; and the additional breathing-organ takes the form of 

 a lung-like sac on each side of the neck communicating with the gill-chamber. 

 Day states that " this amphibious fish, when kept in an aquarium, may be 

 observed constantly rising to the surface for the purpose of respiring atmospheric 

 air direct. It usually remains with the snout close to the surface, and in like 

 manner lies in the grassy sides of ponds and stagnant pieces of water, so that 



