CHAPTER XXII 
THE APODES, OR EEL-LIKE FISHES 
wahi/HE Eels.—We may here break the sequence from the 
‘ie i Isospondyli to the other soft-rayed fishes, to inter- 
S}| 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 (a@, without; zoids, 
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 vertebre, 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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