48 
POPULAR SCIENCE REVIEW. 
development. We find in some special developments of tlie 
fins, or of parts of them, as in the case of the pectorals of the 
Flying Gurnards (Dactylopterus) , and the separate filaments of 
the ventrals in the true Gurnards ( Trigla ) ; or certain of the 
fins undergo a change of position and function, as in the so-called 
Pediculati, of which the Fishing-frog or Sea Devil ( Lophius 
piscatorius) may he taken as an example, in which, by an elon- 
gation of the carpal hones into a sort of arm, the pectoral 
fins, originally widely expanded, lateral organs, are converted 
into something very like feet, upon which the fishes rest and 
move about at the sea-hottom. The young Fishing-frog, in 
fact, although presenting a considerable family likeness to its 
parents, differs from them in some respects very remarkably, 
especially in the great development of the pectoral and ventral* 
fins, in the curiously-branched structure of the free dorsal spines 
behind the filament which hears the so-called * bait ’ immediately 
over the mouth, and the great elongation of the fin-rays in 
general, which are for the most part produced into long filaments. 
Similar filamentious prolongatons of some of the fin-rays occur 
in many other young fishes, and most strikingly in some of 
those curious inhabitants of deep water, the Ribbon fishes, the 
young of which are frequently captured at the surface, although 
the adults have never been met with there, except in a dead or 
dying condition. The young of Trachypterus, a genus of Ribbon 
fishes, examples of one species of which (the Deal-fish, Tra- 
chypterus arcticus) are generally thrown upon the northern 
coasts of Britain after the equinoctial gales, exhibits this pro- 
longation of the fin-rays in a most striking manner. The adult 
fish, which may attain a length of six feet, and which has a 
body shaped like a thin, broad, tapering blade, has a dorsal fin 
extending the whole length of its back, but with the foremost 
portion, situated above the head, separated from the rest of the 
fin, above which it rises to a considerable height, being supported 
upon very long flexible spines. The pectoral fins are small ; 
the ventrals, situated beneath them, long, and supported by few 
rays ; whilst the tail terminates in an obtuse tip, from the dorsal 
surface of which the caudal fin rises, nearly at right angles 
to the long axis of the body. In the young Trachypterus , 
which is also a thin, flat-sided fish, having a dorsal fin running 
the whole length of its back, the caudal fin, which is consider- 
ably larger in proportion than in the adult, is set on the tail in 
the usual way; the rays in the front portion of the dorsal, 
above the head, are enormously prolonged, forming free fila- 
ments, extending to three or four times the length of the body 
of the fish, and having in their course numerous lappet-like 
dilatations; the rays of the ventral fins are also considerably 
produced. 
