62 Adaptations of Fishes 
To this in the process of specialization greater complexity has 
been added. 
The luminous organs of some fishes resemble the supposed 
original structure of the primitive photophore, though of 
course these cannot actually represent it. The simplest type 
of photophore now found is in Astronesthes, in the form of 
irregular glandular luminous patches on the surface of the skin. 
Fie. 47 —Argyropelecus olfersi Cuvier. Gulf Stream. 
There is no homology between the luminous organs of any insect 
and those of any fish. 
Photophores of Porichthys.—Entirely distinct in their origin 
are the luminous spots in the midshipman (Porichthys notatus), 
a shore fish of California. These have been described in detail 
by Dr. Charles Wilson Greene (late of Stanford University, now 
of the University of Missouri) in the Journal of Morphology, 
xv., p. 667. These are found on various parts of the body in 
connection with the mucous pores of the lateral lines and about 
the mucous pores of the head. The skin in Porichthys is naked, 
and the photophores arise from a modification of its epidermis. 
Each is spherical, shining white, and consists of four parts—the 
