PHYSIOLOGICAL 429 



we have to deal with a widespread pecuHarity in metabohsm, 

 expressive of high intensity of Hfe, which has been seized upon in 

 different types for different uses and elaborations. 



In course of his long and varied investigations into luminescence. 

 Prof. Dubois has expressed the hope, in principle quite rational, 

 that a mastery of its secrets, chemico-physical, bacterial, etc., may 

 some day lead to practicable and highly economical utilisations 

 for lighting purposes. It must be said that no less unexpected and 

 remarkable applications of bacteriology and of biochemistry are 

 already famiUar to us, while others are in the stage of active inquiry. 

 It is as yet but a dream, yet by no means a wholly absurd one, 

 that from the ranks of such resourceful and untiring workers may 

 yet emerge for us even rival companies of lamp-lighters, surviving 

 by economy of energy over their predecessors; and why not even 

 more pleasing too ! 



Special Case of Bio-Luminescence. — Of most luminous fishes 

 three things may be said: (i) that their production of light must 

 be of use to them, since it is associated with elaborate organs, 

 often suggestive of eyes; (2) that their luminescence is intrinsic 

 and not bacterial; and (3) that they are intra-luminescent, oxidising 

 their photogenic material within the cells of the luminous organ. 



To the last statement, a single exception is at present (1930) 

 known, namely a fish called by the unprepossessing name Malaco- 

 cephalus laevis, which might be translated "Smooth Softhead", 

 surely not a happy name for a creature that, as we shall see, has 

 almost succeeded in making a halo for itself. It belongs to the 

 Macruridae, a family closely allied to the Gadidse, which includes 

 cod and haddock, hake and ling. It is a common fish along the 

 outer edge of the continental shelf from Ireland south to Morocco, 

 and is taken in considerable numbers by fishermen who trawl for 

 hake in waters of over 150 fathoms. A few small specimens struggle 

 into shallower water off Galway and the Fastnet. There is nothing 

 very remarkable in its appearance except the contrast between 

 the very long whip-like tail and the short thick body. But its 

 luminescence, discovered in 1925 by Mr. C. F. Hickling, is unique. 

 (See Journ. Marine Biol. Assoc, Oct. 1925.) 



On the under surface of the "Softhead's" body there is the 

 luminous organ which Mr. Hickling was first to notice. It consists 

 of a folded or plaited area of glandular skin, which has sunk into 

 the musculature of the body-wall, between and behind the pelvic 

 fins. This area forms a compact gland with a flat wide duct, out of 

 which there come at intervals little luminous clouds — the oxidation 

 occurring outside the body. There is no evidence of the luminosity 

 being due to bacteria living within the tissues of the fish; on the 

 contrary, the evidence confirms the interpretation that luciferin is 

 rapidly oxidised into oxyluciferin by a ferment lucif erase. The 



