CHAPTER VII. 

 THE APODES, OR EEL-LIKE FISHES 



HE Eels. We may here break the sequence from the 

 Isospondyli to the other soft-rayed fishes, to inter- 

 polate a large group of uncertain origin, the series 

 or subclass of eels. 



The mass of apodal or eel-like fishes has been usually regarded 

 as constituting a single order, the Apodes (or, without; TTOVS, 

 foot). The group as a whole is characterized by the almost 

 universal separation of the shoulder-girdle from the skull, by 

 the absence of the mesocoracoid arch on the shoulder-girdle, 

 by the presence of more than five pectoral actinosts, as in the 

 Ganoid fishes, by the presence of great numbers of undifferen- 

 tiated vertebrae, giving the body a snake-like form, by the 

 absence in all living forms of the ventral fins, and, in all living 

 forms, by the absence of a separate caudal fin. These structures 

 indicate a low organization. Some of them are certainly results 

 of degeneration, and others are perhaps indications of primitive 

 simplicity. Within the limits of the group are seen other 

 features of degeneration, notably shown in the progressive loss 

 of the bones of the upper jaw and the membrane-bones of the 

 head and the degradation of the various fins. The symplectic 

 bone is wanting, the notochord is more or less persistent, the 

 vertebral centra always complete constricted cylinders, none 

 coalesced. But, notwithstanding great differences in these 

 regards, the forms have been usually left in a single order, the 

 more degraded forms being regarded as descended from the 

 types which approach nearest to the ordinary fishes. From 

 this view Professor Cope dissents. He recognizes several orders 

 of eels, claiming that we should not unite all these various fishes 

 into a single order on account of the eel-like form. If we do so, 

 we should place in another order those with the fish-like form. 



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