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 vertebree 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 cesophagus, and with the anterior vertebre not 
modified. In so far they agree with the Isospondyli. In some 
other respects they resemble the lower Ostariophyst, 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 JIso- 
pondylt 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 Enchelycephalt and Colocephalt), Carenchelt, and Lyo- 
mere. 
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 (iyOus, fish; ce@adn, 
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- 
