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PROCEEDINGS OF THE NATIONAL MUSEUM 



The character of the membranes, spines, and setae of the thoracic 

 legs of the late encysted and recently excysted specimens is given 

 below (for explanation of symbols, see figure 1): 



The above table includes the armature of the thoracic legs of the 

 late encysted and recently excysted forms only. 



Caudal rami of early encysted forms long, conical, length about 

 twice width; attached to posterior end of abdomen. Caudal rami 

 tipped by four plumose setae. Anal region with two long, heavily 

 chitinized, rodlike projections extending posteriorly from genital 

 segment as far as caudal rami. These structures are incorporated into 

 the abdomen of later encysted specimens and do not extend past the 

 posterior end of the abdomen (figs. 20a, b). 



Caudal rami of late encysted and recently excysted forms shorter 

 than those of early encysted specimens, of laminate nature; attached 

 to lateral surface of abdomen. Caudal rami with three long, plumose 

 setae from distal and distal lateral surfaces, one from outer proximal 

 region and one small, plumose seta from outer proximal region (not 

 recorded by Wilson, 1924, for A^. costatus). Inner margin of caudal 

 rami setuliferous (fig. 20c). 



Remaeks. — The peculiar habit of encysting on the fins of teleost 

 fishes exhibited by the male has not been reported previously in the 

 literature for members of the family Pandaridae. The cyst appears 

 to serve as a protective structure for the developing copepod and to 

 replace the normal attachment cord or second antennal attachment 

 of the chalimus stages of other copepods. The encystment of the 

 copepod does not appear to harm the host to any extent and, when 

 the male excysts, the cyst is absorbed by the host. Empty cysts in 

 various stages of absorption were seen on the fins of teleost fishes, 

 some being visible only as a slight irregularity. 



