PHOTOPHORES OF DECAPOD CRUSTACEA 339 



contains a recognizable nucleolus (nl.). At the opposite end of the cell to that occupied 

 by the remains of the nucleus, however, new structures begin to appear. A very 

 delicate vacuolated zone {v.z.) has on its inner side a layer, segmentally arranged 

 (s.z.^), which corresponds precisely in structure and staining reactions to the substance 

 occupying the superficial cells in the photophore of H. novae-zealandiae (Fig. 14, 

 phot.c. 3). 



At c (Fig. 16) the vacuolated zone {v.z.) has extended completely around the inner 

 face of the cell membrane, which now has a fibrous appearance, and the segmented zone 

 {s.z.'^) is also peripherally complete and its segments have extended centripetally. 

 The centre of the " cell " is now occupied by a central body (c.b.) precisely like that seen 

 in H. novae-zealandiae (Fig. 14, c.b.). The similarity of this "cell" to that shown in 

 Fig. 14 {phot.c. 3) is unmistakable, and the radially segmented pattern of the substance 

 of the segmented zone, whether cytoplasm or not, would indicate that the striae seen 

 in the cell in Fig. 14 are in reality indications of segmentation. 



The photogenic cells are separated from each other by walls of connective tissue, in 

 which fine blood channels (Fig. 16, b.c.) are visible. Further strands of connective 

 tissue are seen between the nuclei of the reflector layer (Fig. 15), and the whole region 

 of the photophore is highly vascular. Unlike the condition in the photophore on the 

 fifth thoracic limb of H. novae-zealandiae no indications of innervation were observed. 



The essential similarity of this with the preceding organ is undeniable, and renders 

 more perplexing the inversion of the photogenic tissues already mentioned. Also it may 

 be said in anticipation that the photophores of Systellaspis affinis (p. 354) and S. debilis 

 p. 364), which occupy a similar position behind the base of the last thoracic limb, 

 show an entirely different structure from that in Hoplophonis , being composed of long 

 slender photogenic cells with basal nuclei. 



{d) The carapace photophores of Hoplophorus novae-zealandiae, H. typus, 



and H. grimaldii 

 Well-developed photophores on the outer surface of the branchiostegite of H. novae- 

 zealandiae and H. grimaldii have been observed by Dr Kemp, and their appearance in 

 freshly caught specimens has been recorded in his notes. They are described in H. 

 novae-zealandiae as follows: " On carapace two organs on branchiostegal carina not far 

 from antero-lateral angle, and further back, in posterior half, a curved row of four 

 organs. The foremost of these is situated above the base of the third legs and the hind- 

 most in the blunt projection on the middle of the posterior margin. These six photo- 

 phores are all directed downwards and appear to be well developed structurally. 

 Lower portion (? lens) deep violet blue, succeeded by pale yellow (? photogenic) layer, 

 then by white layer (? reflector), and above all a thick mass of deep red pigment in 

 which dark pyriform bodies, six in a transverse series, can be detected." With regard 

 to H. grimaldii Dr Kemp says: "Luminous organs precisely similar in position and 

 coloration to those of Hoplophorus n.sp. { = H. novae-zealandiae), but the foremost on 

 the lower border of the carapace behind the branchiostegal spine is missing." 



