334 



DISCOVERY REPORTS 



50 



t"- 



-n 



phot. 



c. 



-photc.d.a. 



but at a level just proximal to the nerve ending. Both ends of the muscle loop are 

 attached to the integument of the limb on the side of the photophore remote from the 

 longitudinal muscle. Furthermore, in the pre- 

 paration of the isolated photophore a character- 

 istic nerve ending can be seen on the secondary 

 longitudinal muscle and the muscle loop (Fig. 1 2, 

 n.e.). It is clear that the individual components 

 of the photophore musculature are so placed as 

 to work in opposition to each other, and that 

 they are capable of producing quite complex 

 movements of the whole structure, permitted by 

 what amounts to an arthrodial membrane around 

 the lens. 



The organs at the base of the uropods of 

 Hoplophoriis art very similar to those found in a 

 corresponding position in Systellaspis ajfinis 

 (p. 350 and Fig. 23), and are therefore not de- 

 scribed in detail. The photogenic cells, however, 

 as may be seen by reference to Fig. 13, possess 

 a prominent squarely truncate nucleus, and a 

 basal cap, situated at the proximal end of the 



cell, appears to consist of a finely granular sub- t,. ^ c »u i » n r .u 



' '^'^^ J ° Fig. 13. One 01 the photogenic cells or the 



Stance. The photogenic cells are precisely similar photophore at the base of the uropods of 



to those of the carapace photophores of Hoplo- Hoplophorns typus. n.phot.c. nucleus of photo- 



phorus (p. 339 and Figs. 17, 18). The proximal g*^"''^ ^^"■' phot.cb.c. basal cap of photogenic 



, r 1 1 • 1 1 r • cell; Mo/.c.c/.fl. clear area of photogenic cell; 



granular mass found at their bases, and formmg ^j^^^^^^ p^^^j^^^j g^^„^,^^ ^^^^ ^^ ^^^ ^^ 



there a reflecting surface, is not as in Systellaspis photogenic cell. 



ajfinis, white and opaque, but is translucent and 



appears colourless by transmitted light. These organs possess no tegumental lens and 



no special musculature. 



- — phot.cb.c. 

 -phot. up. 



(b) The organs on the fifth thoracic limb of Hoplophorus novae-zealandiae 

 The fifth thoracic limb of this species bears a luminous patch at the proximal end of 

 the carpus, and a short proximal and a long distal patch on the propodus. With a view 

 to discovering whether these organs followed the same basic structure as those of the 

 pleopods, difi^ering only in the obvious absence of a lens, longitudinal sections of the 

 limb were cut. It was at once apparent that here we have to consider an entirely new 

 type of photophore. The following description is that of the organ on the carpus of the 

 limb, but the other organs are precisely similar. 



The mass of the photophore is made up of a group of cells, presumably the photo- 

 genic cells, which show entirely peculiar features and which give every indication of 

 being cells in various phases of difi"erentiation. Dealing first with the innermost mem- 



