THE COPEPODA 85 



part of the ocular apparatus reaches back into the region of the 

 anterior thoracic somites, and in Cojnlia the pigment-cups enclos- 

 ing the retinal cells lie together in a conical pi'otuberance on the 

 sternal surface of the body. 



Ill this account it has been assumed that the " paired eyes " of 

 Pontellidae and Corycaeidae are derived from the dorso-lateral 

 elements of the nauplius-eye. It must be mentioned, however, 

 that Clans, while admitting this derivation in the case of the 

 Corycaeidae, regarded the lateral eyes of the Pontellidae as homo- 

 logous with the jiaired compound eyes of other Crustacea. If it be 

 the case, however, that in the Pontellid eye, as in those of other 

 Eucopepoda, the retinal cells are " inverted " (or are connected 

 with nerve- fibrils at the end turned towards the light), this 

 homology would seem to be impossible. 



A prol)lematical organ to which a visual function has been 

 attributed is found in the ffeiius Pleuromamma. It lies on one side 



Via. 47. 



Corycaeus nnglicu.'t, male, from the side, sliowinj; one of the large i)aired eyes. L lens; c, 

 crystailine boily ; ji, tubular pigment-cup. (After Leuckart.) 



of the cephalic shield, in the region of the maxillipeds, and consists 

 of a globular i-efractive body enclosed in a mass of pigment, the 

 whole projecting from the surface of the body in a little papilliform 

 elevation. It has also been suggested that this is an organ of 

 phosphorescence, but according to Giesbrecht this is not the case. 



The " (irsthefascs," or "olfactory filaments," of the antennules 

 have already been mentioned. Their number and arrangement 

 vary very much in difierent forms, and atibrd valuable systematic 

 characters. 



The "frontal sense-organs^' are certain sensory setiie, generally 

 a single pair, on the front surface of the head above the rostrum, 

 Avhich are supplied by a pair of nerves arising from the brain, 

 and which have been supposed to be the seat of some special 

 sense. 



The existence of "auditory"' organs in the Eucopepoda is 

 doubtful. A pair of statocysts have been described in the 

 anterior part of the brain in EHcaJanu-^. 



