374 
Fig. 1. Diagrams of the luminous organs of some 
Macrouridae. Coryphaenoides garmani; b, Abyssicola 
macrochtr; c, Coelorhynchus japonicus; d, Coelorhynchus 
hubbsi. phot, luminous organ; an, anus. 
example, C. japonicus has a very short canal 
with the external aperture close to the anus. 
Some species have two scaleless external 
ventral apertures. Examples of this type are 
Malacocephalus laevis (Lowe) and Malaco- 
cephalus nipponensis, each of which has two 
external apertures, one bean-shaped and one 
round. The inner structure is of the normal 
type, i.e., it has a large luminous gland, a re- 
flector, two lenses, and two external aper- 
tures. Their structure has been described by 
both Dr. Hickling and myself. 
The canal is very long in some species, 
such as Coelorhynchus parallelus and C. tokiensis. 
The canal itself functions as a luminous gland 
with a long reflector, a poor lens substance, 
and no external aperture. However, one can 
see the long luminous duct through the 
transparent scales on the lowest part of the 
abdomen. 
PACIFIC SCIENCE, Vol. V, October, 1951 
Fig. 2. Malacocephalus laevis (Lowe), phot, lumi- 
nous organ; an, anus. 
In their young stages these fishes are very 
strange, and only in this stage are they 
strongly luminous, the luminosity being 
visible ventrally as a single line. When full 
grown, this thin duct is covered with black 
pigment, which renders it useless as a lumi- 
nous component in spite of the fact that 
luminous bacteria are living within it. The 
luminosity of Coelorhynchus coelorhynchus, as 
described by Hickling (1931), may be due to 
the fact that perhaps he saw a young speci- 
men, as it is probable that this species is very 
similar to the two species under discussion. 
Coelorhynchus hubbsi Matsubara has an ex- 
tremely thin, long canal, each end of which 
is swollen into a club-shaped gland. The 
Fig. 3. Diagram of the luminous organ of Coelor- 
hynchus parallelus and its longitudinal section, phot, 
luminous gland; refl, reflector; cond, conduit; chr, 
chromatophore; an, anus; rect, rectum. 
