Adaptations of Fishes 59 
of electric fishes, is not an eel, but allied rather to the sucker or 
carp. It is, however, eel-like in form and lives in rivers of Brazil 
and Guiana. The electric organs are in two pairs, one on the back 
of the tail, the other on the 
anal fin. These are made up 
of an enormous number of 
minute cells. In the electric 
eel, as in the other electric 
fishes, the nerves supplying 
these organs are much larger 
than those passing from the 
spinal cord for any other pur- 
pose. In all these cases 
closely related species show 
no trace of the electric powers. 
Dr. Gilbert has described 
the electric powers of species 
of star-gazer (Astroscopus 
y-grecum and A. zephyreus), 
the electric cells lying under 
the naked skin of the top of 
the head. Electric power is 
ascribed to a species of cusk 
(Urophycts regius), but this 
perhaps needs verification. 
Photophores or Luminous 
Oigans.—Many fishes, chiefly 
of the deep seas, develop 
organs for producing light. 
These are known as luminous 
organs, phosphorescent or- 
gans, or photophores. These 
are independently developed 
in four entirely unrelated 
groups of fishes. This differ- 
ence in origin is accompanied 
by corresponding difference 
fia a 
‘pues oy} UL Surpyyos (s7yvqnb sndovsoysy) 10ze5-1vJQ— SF “OT 
CIPPIMYS “AM UW Aq oy] VOI) 
in structure. The best-known 
type is found in the Iniomi, including the lantern-fishes and 
their many relatives. 
/ 
These may have luminous spots, differ- 
