328 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



The posterior portion of the body of the second 

 nauplius has become somewhat elongated. The 

 caudal end is now truncate or concave rather than 

 rounded. 



The longer setae of the appendages have become 

 plumose in the second nauplius with the addition 

 of fine setules. The appendages remain unseg- 

 mented. The furcal spines do not acquire the 

 distinct barbs reported by Hudinaga (1942) for 

 P. japonini^, but their margins are no longer 

 smooth. 



THIRD NAUPLIUS 



Specimens of the third nauplial stage (fig. 7) 

 ranged in length from 0.45 to 0.49 mm. and from 

 0.17 to 0.20 mm. in greatest body width. Meas- 

 urements were made on 24 specimens raised from 

 eggs. The major differences l>etween this and the 

 preceding stage are the development of 2 distinct 

 furcal processes, the addition of 2 spines on each of 

 these, and differences in the setation and the first 

 sign of segmentation of the appendages. 



The caudal end of the body is now divided into 



2 furcal processes with a distinct notch between. 

 Each furca bears 3 spines, the middle one being ap- 

 proximately two-fifths the length of the body. 

 The external spine measures about one-tliird the 

 length of the median one and the internal spine 

 about one-sixth. The median spine bears minute 

 barbs but the other 2 spines are smooth. The 

 furcal spines are flexed dorsally, as can be seen 

 in lateral view. 



The first antenna has lost its posterolateral seta 

 and now bears 2 lateral and 3 terminal setae. The 

 basal portion of this appendage shows traces of 

 the segmentation that will appear in the next 

 molt. 



The endopod of tlie second antenna has the same 

 complement of setae as in the jireceding stage; 

 liowever, the anteriormost of the terminal setae 

 has grown to almost the length of the others. 



The exopod of the second antenna has added 

 another terminal seta, making a total of 3 lateral 

 and 4 terminal setae. 



The setation of the mandible remains the same. 



Figure 7. — Ventral view of third nauplius. 



