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A. TERAO : 



remaining steadily alive for several seconds. Most frequently it was the 

 photophores in the neighborhood of the eyes that showed this sort of activity; 

 less frequently those of the third or of the sixth abdominal somite. A 

 simultaneous luminescence of photophores in all parts of the body, f. i., such 

 as Doflein 1) (Tafel XVII) has beautifully depicted for AcanthepJiyra debilis, 

 was never observed in the present form. Giving a shake to the water in 

 the vessel containing the crustaceans, all these began the first mentioned 

 sort of illumination. A second shake given to the water immediately after 

 the extinction of the last light at the posterior body end, produced no effect. 

 Nor could the lights be called forth by rubbing or by lightly pressing the 

 crustacean with the finger. However, by crushing it between the fingers a 

 number of the photophores started light just for an instant, producing a 

 sparkling-like effect, but the lights immediately vanished without leaving 

 diffuse lingering luminescence, as the Euphausians do under the same 

 circumstance. By the way, I may mention that the luminescent power of 

 X p7-cJicnsilis was distinctly much weaker than that of the Euphausians 

 which were obtained in the same haul of the collecting net. 



On the morning following the collecting, the specimens oiS. firehensilis, 

 which were kept living, were found to be in apparently good health, being 

 still quite active in their movements. However, when subjected to ob- 

 servation in the dark room, they have entirely failed to show lights. 

 Attempts were made to rouse them into luminescence by external stimuli, 

 but in vain. This may be explained in a general way by assuming that the 

 photophores were in a state of fatigue, and in a concrete way for some, 

 though not all, of them by the fact that the photogenous cells were breaking 

 up, as I have later determined by microscopical examination of the 

 sections. 



Now, as to the structure of the photophores. At the outset I should 

 mention that my material for the morphological study were all fixed early in 



i) Doflein, F., 1914. Tierbau und Tierleben, Bd. II. Das Tier als Glied des Naturganzen. 

 Leipzig und Berlin. 



