ON THE PHOTOGENIC ORGAN OF THE KNIGHT-FISH. 373 



the "sub-ocular" organs of the Anomalopidx and the "sub- 

 mental" organs of the Monocentridx. However, the reservoirs 

 and emissory ducts which are well developed in Monocentris are 

 wanting in both Anomalopsis and Photoblephalon. In the latter 

 all of the several secretory tubules communicate with the external 

 medium by one very short common duct. But each photogenic 

 organ in question is an aggregation of many acinous glands 

 developed in a limited area sub-ocular in position, and the 

 secretory tubules stand vertically and lie parallel side by side 

 as in the case of Monocentris. 



The crystalline deposit is also present. The chromatophores 

 are described as forming a pigment cap which encircles the 

 proximal surface of the organ. 



In Anomalopsis the oral end of the photogenic organ is said 

 to be fastened to a long cartilagous shaft, upon which it is 

 rotated downwards so as to bring the luminous surface against 

 the body wall and thus cut off the light. In Photoblephalon the 

 action of shutting off the light is done by a moveable screen. 

 No analogous mechanisms of light regulation have been found 

 in the submental photogenic organ of Monocentris. 



LITERATURE CONSULTED. 

 Forster, J. 



'14 Zeitschr. f. wiss. Zool., 109, 349-. 

 Harvey, E. N. 



'17 Carnegie Inst., Washington, Pub., 251, 223-. 



'19 The Nature of Animal Light, 69. 



'21 Science, N.S., 53, 314-- 



'22 Carnegie Inst., Washington, Pub., 312, 43. 

 Stead, D. G. 



'06 Fishes of Australia, 89. 

 Steche, O. 



'07 Verh. d. deutsch. zool. Geselsch., 17, 85-. 



'09 Zeitschr. f. wiss. Zool., 93, 349~- 

 Yoshizawa, S. 



'16 Dobutu-Gaku-Zashi, 28, 411. 



