348 



DISCOVERY REPORTS 



On the inner side of the lens and contiguous with it He the radially disposed photo- 

 genic cells (Fig. 21, n.phot.c, cyt.phot.c). Their nuclei are distally situated and are of 

 the form and appearance already noted in Hoplophonis (p. 331), differing conspicuously 



nr.c. 



r. n.photc. phot.c.da. phof.nv 



Ljt.phot.c. 



100^ 



Fig. 21. Section illustrating the structure of the pleopod photophore of Systellaspis affinis. Mallory's triple 

 stain, cut. cuticle; cyt.phot.c. cytoplasm of photogenic cell; gr.z. granular zone; /./. inner layer of lens; l.m. 

 middle layer of lens; l.o. outer layer of lens; n.phot.c. nucleus of photogenic cell; ri.r.c. nucleus of reflector 

 cell ; phot.c.cl.a. clear area of photogenic cell ; phot.l.m. longitudinal muscle of photophore ; phot.nv. photophore 

 nerve; r. reflector. 



