336 RUPERT VALLENTIN AND J. T. CUNNINGHAM. 



acts merely as a reflector. The anterior layer is composed of 

 pellucid polygonal cells, among which are numerous tracheae 

 whose ultimate ramifications end in stellate cells. Schultze 

 found that the tracheal end-cells in the fresh condition reduced 

 osmic acid very powerfully, and he concludes that they have a 

 great affinity for oxygen, and that they are thus the principal 

 agents in the production of the light, though the other cells 

 of the layer are also luminous. At the same time he points 

 out that tracheal end-cells occur in other organs besides the 

 light organs, and wherever they occur powerfully reduce osmic 

 acid. There is obviously at first sight very little agreement 

 between the light organs of the glowworm and the photo- 

 spheria of Nyctiphanes. If we compare the reflectors, we find 

 that of the former, cellular; that of the latter, fibrous. Perhaps 

 the posterior cellular layer of Nyctiphanes is similar to the 

 superficial cellular layer in Lampyris, but then we have not 

 yet proved that the former is luminous. 



We next have to compare the photospheria of Nyctiphanes 

 with the luminous organs of fishes, which have been carefully 

 and ably investigated by R. von Lendenfeld and Professor 

 Moseley. 1 There is nothing in these organs of fishes which 

 resembles the structure seen in Nyctiphanes at all closely. In 

 the fish the phosphorescent organ usually contains structures 

 of two kinds, a system of glandular tubes and a layer of super- 

 ficial specialised epithelial cells. The glandular portion is 

 always the deeper, the epithelial more superficial. Most of the 

 organs have, in all probability, been developed in connection 

 with the slime canal system. The nervous supply as a rule 

 does not present any very striking peculiarity ; there are certain 

 large suborbital organs which are innervated by an enlarged 

 branch of the trigeminus having a special lobe at its origin ; 

 the other organs are supplied by ordinary superficial nerves. 

 There is usually an enveloping capsule with an internal reflect- 



1 ' Report on the Deep-Sea Fishes of the " Challenger," App. A ; ' Report 

 on the Structure of the Peculiar Organs in the Head of Ipnops,' by Professor 

 H. N. Moseley., F.R.S., App. B; ' Report on the Structure of the Phospho- 

 rescent Organs of Fishes,' by R. von Lendenfeld, Ph. D., F.Z.S. 



