288 
POPULAR SCIENCE REVIEW. 
fins supported the view which had previously been arrived at by the author 
to the effect that the paired fins were the specialized and highly developed 
remnants of a once continuous lateral fin on each side ; and on the other 
to decide between the views of Gegenbaur and Huxley, and Thacker and 
Mivart, as to the primitive type of fin-skeleton. The author pointed out that 
the results of his researches were entirely favourable to the view that the 
paired fins were structures of the same nature as the unpaired ; and that 
they gave a more general support to the views of Thacker and Mivart. They 
clearly showed that the pelvic fins retain a more primitive character than 
the pectoral. Conclusions were drawn somewhat adverse to the views recently 
put forward on the structure of the fin by Gegenbaur and Huxley, both of 
whom considered the primitive type of the fin to be most nearly retained 
in Ceratodus, and to consist of a central multisegmented axis with numerous 
rays on its two sides. It appeared, in fact, that the development of the 
skeleton demonstrates that a biserial type of fin like that of Ceratodus could 
not have been primitive, but that it must have been secondarily derived from 
a uniserial type, by the primitive bar along the base of the fin (the basi- 
pterygium) being rotated outwards, and a second set of rays being developed 
on its posterior border. 
(£2 x < 
//. y.a. 
v 
