PHOTOPHORES OF DECAPOD CRUSTACEA 



343 



The foregoing information elicited from a study of serial sections renders intelligible 

 the appearance of the carapace photophores in superficial view. In all three species 

 studied the organs are readily visible in specimens stored in formalin, and since those 

 of H. typiis were most clearly defined in my specimens in this view they will be described 

 as a typical example of the organs. In this species the organs have the form of five 

 short amber-coloured streaks, two of which are situated anteriorly and three posteriorly 

 on a line curving upwards and backwards from the antero-ventral margin of the cara- 

 pace. The whole carapace is lightly dotted with contracted carmine chromatophores, 

 but these are most numerous around the photophores, where they form a loose dorsal 

 cap to the photogenic cells. The lens is seen as a white bar ventral to the photogenic 

 cells, and is most apparent in the anterior pair of photophores, which are more highly 

 diff^erentiated than the posterior three. Using a moderately high power, a faint white 

 cloudiness was seen in the basal parts of the clear areas of the photogenic cells. This was 

 not seen in the other species examined, nor in the sections. It is not easy to say at this 

 stage whether this was due to a precipitate caused by fixation and preservation in 

 formalin, or whether on the other hand the emptiness of the photogenic cells previously 

 stressed is evidence of imperfect fixation and preservation. 



photcnv. 

 n.chif.ep. 



bv. 



phof.c.da. 



n.r.c. 



n.rc. 



n.chif.ep. 



lOOjj. 

 Fig. i8. Semi-diagrammatic external view of the most anterior left carapace photophore of Hoplophorus typus. ab 

 represents a plane of section corresponding to that of Fig. 17. The vertically striated area is the lens; the remainder of 

 the integument is assumed for the purpose of the figure to be entirely transparent and is not shown, b.v. blood vessel; 

 /. lens ; n.chit.ep. nucleus of chitogenous epithelium ; n.r.c. nucleus of reflector cell ; phot.c.cl.a. clear area of photogenic 

 cell ; phot.c.nv. fibres innervating photogenic cell. 



