Notes on the Photophores of Sergestes 

 prehensi/is Bate. 



• By 



Arata Terao, Rigakushi. 



Zoological Institute, Science College, Tokyo Imperial University. 



With J figures in text. 



The photophores of decapod Crustacea have received much illumination 

 from the researches of Kemp 11 ('io a and b). Sergestes challengeri Hansen, 

 amongst some others, was studied by him with great care as regards that 

 organ. Now, my own studies of a decapod crustacean of the same genus, 

 which I identify with 5". prehensilis of Bate, have shown that it is in 

 possession of photophores apparently agreeing in essential structure with 

 those known from certain other crustaceans, but especially closely with 

 those of J>. cha/lengeri as described by Kemp, although I stand at variance 

 from him in many points with respect to the interpretation of the parts. 



Bate 2) ('88), the original describer of S. prehensilis, and Hansen 31 ('03), 

 who re-examined the species, have both made no mention of the photo- 

 phores. The organ loses its pigments in most preservative fluids and is 

 thus rendered inconspicuous, so that it may easily remain unnoticed unless 

 a special search be made for it. In the fresh specimens and in certain 

 conditions of preservation, the photophores can without difficulty be 

 observed with the naked eye as minute reddish spots located at definite 



1) Kemp, S, igio a. The Decapoda Natantia of the Coasts of Ireland. Fish. Ireland &c. 

 Invest, for igo8, no. I. Ditto, igio b. Notes on the Photophores of Decapod Crustacea. 

 P. Z. S., 1910, pt. m. 



2) Bate, C. S., 1888. Report on the Crustacea Macrura dredged by H. M. S. Challenger during 

 the years 1873-1876. 



3) Hansen, H. J., 1903. On the Crustacean of the Genera Petalidiwn and Sergestes from the 

 ' Challenger' with an Account of Luminous Organ in Sergestes rfialktigeri, n. sp. P. Z. S. 



