PHOTOPHORES OF DECAPOD CRUSTACEA 



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This muscle is definitely though faintly striated at some distance from the photophore 

 (Fig. II, phot.l.m.s.), but nearer to it the striae progressively disappear and the fibres 

 become sinuous and twisted. This unstriated portion I have called the attachment of 

 the longitudinal photophore muscle (Figs. lo, ii, phot.l.m.a.), although it is true that 

 it has little of the normal appearance of crustacean muscle attachment. It clearly functions 

 as a tendon of the muscle. Although the main portion of the longitudinal muscle lies 

 in the situation described there extends from it a mass of connective tissue forming an 

 incomplete sheath around the organ. In the connective tissue lie a number of muscle 

 strands, some of which are condensed into a smaller secondary longitudinal muscle 

 on the opposite side of the photophore (Fig. 12, phot.lm'.). This can be clearly seen in a 

 photophore carefully dissected out from the surrounding tissues. In addition, in both 

 the serial sections and the isolated photophore, a loop of muscle (Figs. 10-12 and 

 Plate XXV, fig. I, phot.m.l.) encircles the organ almost completely. It lies equatorially 



Fig. 12. A pleopod photophore of Hoplopkorus grimaldii, dissected from the Hmb and seen in whole view, 

 showing the arrangement of the musculature, chit, chitin; n.e. nerve ending on photophore musdc; phot.c. 

 photogenic cell; phot.lm. longitudinal photophore muscle; phot.l.m'. secondary longitudinal photophore 



photogenic cell; phot 



musde;ph(jl.m.l. photophore muscle loop; phot. nv. photophore nerve 



4-2 



