190 



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. 





FIG. 145. 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 



