THE TRUE FISHES. 175 
other known bony fishes in having six pairs of internal bra -chial clefts, 
and consequently five pairs of gills. It has no swimming-bladder, 
Fic. 217.—Argyropelecus hemigymnus, twice natural size, snowing groups 
“ ’ of luminous organs. 
Fic, 218.—The Pelican fish (Zurypharynx pelecanoides). 
