140 The Apodes, or Eel-like Fishes 



It is probable, though not absolutely certain, that the Apodes 

 are related to each other. The loss among them, first, of the con- 

 nection of the post-temporal with the skull; second, of the 

 separate caudal fin and its hypural support ; third, of the distinct 

 maxillary and premaxillary ; and fourth, of the pectoral fins, must 

 be regarded as successive phases of a general line of degradation. 

 The large number of actinosts, the persistence of the notochord, 

 the absence of spines, and the large numbers of vertebrae seem 

 to be traits of primitive simplicity. Special lines of degenera- 

 tion are further shown by deep-sea forms. What the origin 

 of the Apodes may have been is not known with any certainty. 

 They are soft-rayed fishes, with the air-bladder connected by 

 a tube with the oesophagus, and with the anterior vertebras not 

 modified. In so far they agree with the Isospondyli. In some 

 other respects they resemble the lower Ostariophysi, especially 

 the electric eel and the eel-like catfishes. But these resem- 

 blances, mainly superficial, may be wholly deceptive; we have 

 no links which certainly connect the most fish-like Apodes 

 with any of the other orders. Probably Woodward's sugges- 

 tion that they may form a series parallel with the Iso- 

 pondyli and independently descended from Tertiary Ganoids 

 deserves serious consideration. Perhaps the most satisfactory 

 arrangement of these fishes will be to regard them as constitut- 

 ing four distinct orders for which we may use the names Sym- 

 branchia (including Ichthyocephali and Holostomi), Apodes (in- 

 cluding Enchelycephali and Colocephali), Carencheli, and Lyo- 

 meri. 



Order Symbranchia. The Symbranchia are distinguished by 

 the development of the ordinary fish mouth, the maxillary and 

 premaxillary being well developed. The gill-openings are very 

 small, and usually confluent below. These fresh-water forms 

 of the tropics, however eel-like in form, may have no real 

 affinity with the true eels. In any event, they should not be 

 placed in the same order with the latter. 



The eels of the suborder Ichthyocephali (ix&v?, fish ; Ke(f)a\i}, 

 head) have the head distinctly fish-like. The maxillary, pre- 

 maxillary, and palatines are well developed, and the shoulder- 

 girdle is joined by a post-temporal to the skull. The body is 

 distinctly eel-like, the tail being very short and the fins incon- 



