FINS OF ELASMOBRANCHS. 461 
seems to indicate that he is disposed to consider them to be derivatives from the axial 
skeleton—as formed, perhaps, from modifications of diverging appendages of the ribs, 
i. é. from rib-elements proceeding out laterally. He thus more or less returns, if I have 
not misunderstood him, towards Goodsir’s speculations. 
According to these various naturalists, the paired fins of fishes are derivations from 
the axial skeleton or from the branchial arches, being of the nature of productions 
ventrad or externad from such internal parts. Some of the authors cited regard the 
skeleton of the limbs as essentially similar to that of the azygos fins. Such are Maclise, 
Humphrey, Macalister, and (not certainly) Goodsir. 
Professors Owen and Gegenbaur, on the contrary, consider the paired and azygos 
limbs as fundamentally different skeletal structures; and Cuvier and Professor Huxley 
also appear to have shared this view. I do not recollect to have heard or read any 
distinct statement by Professor Huxley on this subject; but in his ‘ Anatomy of 
Vertebrates’! he speaks of ‘‘ the interspinous cartilages or bones,’ of “ the median 
fins,” as “ as cartilaginous or osseous elements of the exoskeleton.” 
The further fundamental distinctness between the paired limbs and the axial 
(including the branchial) system appears to have been a view entertained by Cuvier 
and also by Professor Huxley. I have myself distinctly enunciated the same view in 
1870’; and later* I have declared my conviction ‘‘ that the appendicular skeleton is no 
mere portion of the axial skeleton, but a distinct system of parts appended to and more 
or less closely and variously connected with the axial system.” To this conviction 
I now adhere more firmly than ever. 
As with the limbs, so also the azygos fins may be, and have been taken to be, either 
parts of the axial skeleton, or parts fundamentally distinct therefrom. ‘The third pos- 
sibility that they may be partly axial and partly peripheral, is an opinion which I 
believe has not been entertained hitherto by any one. 
The first view (that they are essentially axial) has been held by Geoffroy St.-Hilaire * 
and Maclise, probably by Professor Goodsir, and certainly by Professor Gegenbaur, 
who tells us° that their skeletal supports, “‘erscheinen im einfachsten Zustande als 
Gliedstiicke bedeutend ausgedehnter oberer Domfortsatzbildungen, die unter Ablosung 
vom Wirbel zu grésserer Selbstandigkeit gelangen.” 
The doctrine of the distinctness of these parts from the axial system appears to have 
had the sanction of Cuvier; and it has been taught by both Professors Owen and 
Huxley that the solid supports of the azygos fins were exoskeletal structures ; and this 
view I have myself held and put forward °. 
Altogether, then, the following views have been held :— 
1 1871, page 43. - ? Linnean Trans. yol. xxvii. p. 388. 
3 Lessons in Elementary Anatomy, 1873, p. 230. 4 Mémoires du Muséum, vol. ix. 1822, p. 89. 
° Grundriss d. yergl. Anat. p. 488. ° Lessons in Elementary Anatomy, p. 275 
