108 CLASSIFICATION" OF FISHES. 



■which the uniformity of this structure is preserved. 

 We can now add to these proofs others, equally strong, 

 presented by the reptiles and the fish. A great and 

 peculiar development of the tail pervades the whole of 

 the order Apodes, and of all other groups by -which it 

 is represented ; so that^ by designating this type^ when 

 speaking of fishes, as the anguiiliform, instead of the 

 rasorkd, the reader will immediately be reminded of 

 the eel-shaped form, which is its chief characteristic. 

 By the tail, we do not, of course_, mean the caudal fin ; 

 for that, in the fishes we are now speaking of, is 

 usually very small ; and, among several, it is sometimes 

 wanting. The true tail of a fish, strictly speaking, 

 commences with the termination of the stomach ; 

 the length of the latter being manifested, externally, by 

 the situation of the vent. The abdomen of the eels 

 is so unusually short, as not to equal one fourth 

 the length of the tail ; and this structure is just as 

 prevalent in groups which represent the apodal order 

 as in the order itself. Thus, although there seems but 

 one character of the rasorial type of birds to be traced 

 also in that of fishes, yet it is the principal one, and it 

 is so universally prevalent, as to render the presence of 

 others unnecessary to detect the analogy. The only 

 instance yet ascertained of the scansorial power being 

 possessed by fish, is that of the Perca scandens, which 

 is said to climb b?.nks and aquatic plants by using its 

 pectoral spines as feet. 



(97.) We shall now state a few of the modifica- 

 tions under which the anguiiliform type appears in 

 such groups as represent, without belonging to, the 

 apodal order; all being distinguished, as just observed, 

 by having the abdomen much shorter than the tail. In 

 the eels, the body is cylindrical; but in naany other 

 analogous famiHes it is compressed, and that to such an 

 extent, as to have given rise to Cuvier's expressive name 

 of riband-fish. The genera Cepola, LeptocephaluSj OpM- 

 dium, &c. are good illustrations of this structure ; not to 

 mention such extraordinary forms as the Gymnocephali 



