xxn APODES 599 



of filling with air immediately derived from the atmosphere. 

 Although covered over by the common integuments, these bladders 

 present externally, when inflated, two protuberances of a round 

 shape. Of the whole volume of blood contained in the branchial 

 artery, one-third passes through the gills and respiratory bladders, 

 whilst the other two-thirds are conveyed directly from the heart 

 to the aorta without being exposed to the action of the air. 1 

 This amphibious Fish, when in the water, constantly rises to the 

 surface for the purpose of respiration, and it is often found lying 

 in the grassy sides of ponds after the manner of Snakes. 



Sub-Order 4. Apodes. 



Air-bladder, if present, communicating with the digestive tract 

 by a duct. Praemaxillaries absent ; the maxillaries, if present, 

 separated on the median line by the coalesced ethmoid and 

 vomer. Pectoral arch, if present, not connected with and remote 

 from the skull ; mesocoracoid arch absent. Fins without spines, 

 the ventrals absent. Anterior vertebrae distinct, without Weberian 

 ossicles. 



The Apodes or Eels are elongate, serpentiform Fishes with 

 naked skin, or with minute scales imbedded in the skin, the 

 opercular bones small and completely hidden under the integu- 

 ment ; narrow or minute gill -openings ; the vertical fins, if 

 present, confluent behind or separated by the projecting tip of the 

 tail. The pterygo-palatine arch is often reduced or absent, and 

 there is no distinct symplectic ; the supraoccipital bone is small, 

 separated from the frontals by the parietals, which meet on the 

 middle line. The vertebrae are very numerous (up to 225), and 

 the praecaudals bear strong parapophyses, to which short, slender 

 ribs may be attached ; epineurals are sometimes present. The 

 five families into which this sub-order is divided show remarkable 

 degrees of simplification of the skull, through reduction or loss 

 of either the maxillary or the pterygo-palatine arches. 



There has been much difference of opinion in the determina- 

 tion of the bones of thre upper jaw in these Fishes. Cuvier regarded 

 the lateral bones of the upper jaw as praemaxillaries, Owrn and 

 Eichardson as palatines (at least in Muraenas), whilst Peters 



1 Cf. Taylor, Edirib. Journ. Sci. v. 1831, p. 33; Hyrtl, Denkschr. Ak. //'/-//. 

 xiv. 1858, p. 39. On the osteology, cf. Gill, Proc. U.S. Nat. Mas. xiii. 1890, p. 299. 



