492 THE WONDER OF LIFE 



Some of them are simple, but others have a comphcated 

 optical apparatus with some or all of the following structures 

 — ^pigment layer, reflector, lens, and diaphragm. While 

 we may say that the production of hght is parallel to the 

 production of heat in a muscle or of electric discharges in 

 Torpedo, there must be some definite utility when the organs 

 have a comphcated apparatus. Very noteworthy is the 

 remarkable economy of the illuminant ; a quite infinites- 

 imal proportion of the energy is wasted on the production 

 of heat. 



In two surface fishes of the Malay Archipelago, 

 Anomalops hatoptron and PhotoblepharonpalpebraUs, studied 

 by 0. Steche (1909), there are very large lumiaous organs 

 about the head, which seem to give out a constant light 

 without requiring any particular stimulus. The lumin- 

 escence has its seat in material secreted by glandular cells, 

 and occurs outside the cells in the cavity of the gland which 

 they form. In the fishes we have mentioned, the lumin- 

 escent organ can be, so to speak, extinguished by a down- 

 ward movement, which possibly takes place when an enemy 

 appears on the scene. 



Messrs. Holt and Byrne describe a remarkable deep-water 

 fish, Lamprotoxus, from the south-west coast of Ireland. 

 It bore a filamentous barbule many times longer than the 

 body. The colour of the scaleless skin was velvety- 

 black and the barbule was grey. A purphsh-grey cord-hke 

 band of luminous tissue, partially embedded in the skin, 

 formed a closed loop on the anterior part of the body. 

 There was also a large photophore behind and shghtly 

 below the eye, occluded by skin save for a narrow slit ; 

 and there were numerous very small photophores. 



There is httle direct evidence as to the use of luminescence. 



