362 



DISCOVERY REPORTS 



the nuclear mass have a prominent nucleolus and show an irregular chromatin reticu- 

 lation. The mass of nuclei is bounded on its inner side by a continuation of the con- 

 nective tissue sheet (Fig. 28, c.t.), and connective tissue fibres, continuous with those 

 of the sheet, penetrate the mass and are found among its nuclei. 



The basement membrane underlying the chitogenous epithelium can be traced for 

 some distance into the mass of nuclei, and although it becomes very tenuous and con- 

 fused with connective tissue fibres it appears to cut off those nuclei derived from the 

 chitogenous epithelium from the inner nuclei of different appearance. It would there- 

 fore appear that these inner nuclei are of mesodermal and not of ectodermal origin, 

 but it is not possible to state what is their precise derivation. 



No thickening of the integument in the shape of a lens-like structure is apparent 

 over the mass of nuclei, and nothing in the appearance of the whole organ when com- 

 pared with the appearance of known photophores definitely suggests that it too may be 

 luminous. It can only be said that if these structures are truly luminous organs then 

 they are of an essentially different form and are simpler than those found elsewhere in 

 the body. It is possible that they are merely dense masses of chromatophores with no 

 power of light production, but this can only be verified by future observations on living 

 animals. 



cut. 



chit 



n.chitep. 



n.cf 



Fig. 28. Part of a transverse section through the base of the telson of Systellaspis affinis to show one of the structures associated 

 with red pigment spots during Hfe. Mallory's triple stain, b.m. basement membrane; chit, chitin; c.t. connective tissue ; 

 cut. cuticle ; n.c.t. connective tissue nucleus ; ti.chit.ep. nucleus of chitogenous epithelium ; n.m. nucleus of subintegumental mass. 



