350 



DISCOVERY REPORTS 



(b) The iiropod photophores 

 Complex photophores of the same basic pattern as that shown by the pleopod 

 photophores, but presenting a curious condition of the photogenic cells, occur im- 

 mediately in front of the bases of the uropods of Systellaspis affinis (Figs. 20, 22, phot.ur. 

 and Plate XXVI, fig. i). They are elevated on slight but definite protuberances which face 

 downwards and backwards, and, being without any trace of a controlling musculature 

 or peripheral depression circumscribing the lens, appear to be immovable. They are 

 innervated by a pair of massive nerves (Fig. 22, phot.nv.) which arise from the ventral 



nhr.alc. 



v.n.c. 



phot.nv. 



phot ur. 



v.n.c. 



Fig. 22. Transverse section through the junction of the sixth abdominal somite and telson of Systellaspis 

 affinis to show the position and innervation of the uropod photophores. X33. al.c. alimentary canal; 

 c. cavity appearing in the section due to the slight overlapping of the telson by the sixth abdominal somite at 

 their junction; ?n. abdominal muscles; n.br.al.c. nerve from ventral cord to alimentary c-in^X; phot.nv. nerve 

 to photophore;/)/?o/.!«-. photophore immediately in front of uropod base; v.n.c. ventral nerve cord; v.n.c' tip 

 of a posteriorly directed fold of the ventral nerve cord appearing in the section. 



