370 YO K. OKADA. 



Malayan Sea, and the photogenic organs of these fishes closely 

 resemble those of Monocentris (see Steche, 1909, p. 349). No 

 granules have, however, been detected in the cells of the latter. 

 I am rather of the opinion that the granules are produced through 

 the metamorphosis of the cytoplasm at the time of cellular 

 destruction as Forster (1914) has described in Pholas dactylus. 

 On the other hand, Harvey (1921, p. 43) claims the granular 

 bodies in the tubules to be symbiotic bacteria which cause the 

 luminescence. To this problem I shall return on another 

 occasion. 



The secretion produced in the way just considered is carried 

 from the tubules toward the medullary part of the organ through 

 a number of tubules of the second order, or the "collecting 

 tubules" (Fig. 4, col}. The latter proceed more or less parallel to 

 one another but separated by irregular trabeculae of connective 

 tissue. They communicate often in their course and finally at 

 the centre of the organ constitute several large lumina, or the 

 "reservoirs" (Figs. 2 and 3, rs~), in which the secretion is stored 

 and probably oxydized with light production. The reservoirs 

 communicate also with the outer medium by a number of long, 

 well-defined, parallel tubes, or the "emissory ducts" (Figs. 2 

 and 3, dt). About nine such ducts are generally observed. 



The inner walls of the collecting tubules and reservoirs are 

 lined by a low, simple epithelium, while those of the emissory 

 ducts are covered by one which is stratified, a direct continuation 

 of the epidermis of the surface. 



Beyond the tubular area the gland proper the photogenic 

 organ is enclosed externally by a thick dermal layer in which a 

 great number of chromatophores are found. The latter are 

 especially abundant on the outer surface of the organ. However, 

 they are scattered and do not constitute a pigment cap (Figs. 2 

 and 3, chr). 



The blood is supplied by branches of the lower jaw arteries 

 which run near the organ. They enter into the gland proper, 

 passing through the surrounding dermal tissue, and on reaching 

 the tubular area branch out all at once into many capillaries, 

 each making its way between the secretory tubules. After 

 passing the tubular region the capillaries gather themselves again 



