REPORT ON THE DEEP-SEA FISHES. 325 



a certain extent. These elements are evidently modified gland-cells, and the shining 

 vesicle represents the secretion. Although such cells are produced, the ordinary 

 undifierentiated gland-cell is not dispensed with. These typical clavate cells are always 

 found in connection with undifferentiated glands. 



The slender cells which support these clavate cells may have been derived from the 

 fibrous layer surrounding the gland-tubes. 



The light reflecting spicule layer is apparently a modified inverted scale.^ 



The glands themselves are not to any extent difi"erent from other slime-glands found 

 in fishes. 



The only doubtful structures which remain are the yellow bodies in Halosaurus, and 

 these may with great probability be regarded as a secretion. We may, therefore, sum 

 up as follows : — 



1. The phosphorescent organs of fishes are more or less modified glands, which 



have partly been developed from simple slime-glands in the skin, and partly 

 in connection with the slime-canal system. 



2. The typical clavate cells are modified gland-cells. 



3. The accessory refiectors and sphincters are developed from the shin around and 



below the gland. 



4. TJie large suborbital organs are innervated by a modified branch of the 



Trigeminus, and the other organs by the ordinary superficial nerves. 



c. The Phosphorescent Organs of Fishes compared with those of some 



Other Animals. 



Among Coelenterates, particularly the higher species, there are a great number of 

 forms which are known to produce light. Among Sponges no such observations have 

 been recorded, but in the other groups such instances are numerous. Special organs are 

 not, however, developed for phosphorescent purposes, but the ordinary slime produced 

 by the gland-cells in the epithelia is luminous, the light being apparently emitted 

 independently of the will of the animal. This is the lowest form of phosphorescence 

 hitherto observed among Enterozoa. 



A higher form is represented by Phyllirhoe bucephala,^ where a great number of 

 spherical cells scattered throughout the body emit light. These cells, which contain an 

 oval, flattened nucleus and a large spherical vesicle filled with a highly refracting sub- 

 stance, have been compared above to the clavate cells in fishes. They are scattered and 

 isolated and are attached by granular threads to ganglion cells. The organs are under 



' According to C. Emery, Mittheil. aus d. znol. Station zu Neapel, vol. v. 



■^ Paolo Panceri, AM Accad. Sci. Fis. e Mat. Napoli, vol. v. No. 14. E. Miillcr, Bau der Phyllirhtie, Zeitschr. /. 

 roiss. ZooL, 1854. 



