PHOTOPHORES OF DECAPOD CRUSTACEA 



369 



of this work makes some means of ready comparison between them a necessity. The 

 following tabular view, having reference only to some of the photophores occupying a 

 common position in the different members will, it is hoped, be of some assistance. 



* Hoplophorus novae-zealandiae, H. grimaldii and H. typus. E. Elongated photogenic cells, with basal 

 nucleus and area devoid of cytoplasm. L. External lens. I.C.L. Intracellular lens. R. Radially seg- 

 mented granular spheres ("rosettes"). W. White granular substance. C.B. "Central body" present, 

 white granular substance absent. 



VI. DISCUSSION 

 The discovery of small subcuticular structures, almost certainly luminous in function, 

 in Sergestes regalis adds to the variety of photophores found in members of this genus. 

 In his notes made on board the 'Discovery', Dr Kemp records the positions of about 

 230-240 purple spots which mark the situation of these presumed photophores, and it 

 is interesting to observe that, as in S. challengeri and its close allies, as well as in S. 

 corniculum, S. sargassi, S. diaponthis, and S. edivardsi (p. 320), some, in this case a row 

 of seven to eight, are found in the roof of the branchial chamber. The peculiarity of 

 this situation will be mentioned again later in this discussion. It is evident that the 

 photophores described by Kemp (19 10 6) in 5. challengeri, and in S. lucens (Terao, 19 17, 

 as S. prehensilis, see Gordon, 1935, p. 308), ahhough showing some differences from 

 each other, are actually fundamentally similar. The differences noted by Terao, such as 

 the presence in S. hice?is of a basement membrane beneath the photogenic cells and of a 

 distinct lens epithelium, and their absence in 5. challengeri, may perhaps be accounted 

 for by the differences in fixation and preservation of the specimens employed by these 

 two authors. Terao admits that some disintegration had taken place in his specimens 

 before fixation. In any event the photophores of these two species differ profoundly 

 from those of S. regalis. Whereas in the two former species {S. lucens and S. challengeri) 

 large cells with prominent nuclei, which are without doubt photogenic, occur beneath a 

 well-defined two-layered lens, in the latter species the structures which I have referred 

 to as "photogenic centres" are very different and are not readily interpreted as cells. 

 Furthermore, a lens is absent from these photophores. 



