PHOTOPHORES OF DECAPOD CRUSTACEA 



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below, and red above. But, as may be seen from the description of the organs in 

 Parapandalus, the minute structure of the organs of the Penaeid and the Carid show 

 divergences which might be expected from the systematic position of these forms and 

 which can only indicate physiological differences, probably profound, in the mode of 

 effecting whatever function, production of luminescence or not, the organs subserve. 

 The independent acquisition of such organs, so closely similar in their grosser features, 

 in unrelated Decapods is truly remarkable, and may be taken to indicate that they are 

 of some profound significance in the life of the animals. That this significance is the 

 production of light is suggested by their coloration, which resembles that of known 

 Decapod photophores, by their position with respect to the branchial chamber, and by 

 Dana's remark concerning the phosphorescence of Thalassocaris lucida. 



2. THE PIGMENTED SPOTS ON THE PLEOPODS 

 When the first three pairs of pleopods of Parapandalus were examined with the 

 object of discovering whether any organ was associated with the deep red spot at the 

 base of the endopod, referred to in Dr Kemp's notes, no trace of pigment remained, and 

 in superficial view no unusual structure could be detected. Accordingly, two of the 

 pleopods were sectioned, and careful search revealed the presence, in the precise 

 position described as occupied by the red spot, of the organ illustrated in Fig. 9. 



Fig. 9. Longitudinal section through the base of the endopod of the first left pleopod of Parapandalus 

 richardi, showing the structure corresponding with the position of a deep red pigment spot in the living 

 animal. Fixed Duboscq, Delafield's haematoxylin and eosin. chit, chitin of the limb; c.t. connective tissue; 

 haem., haemocoele; n.c.l.c. nucleus of connective tissue cell; n.chit.ep. nucleus of chitogenous epithelium; 

 pl.m. pleopod muscle. 



