142 



BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



nearly to the broad sphincter muscle of the upper lip. The oral 

 muscles proper differ from those of the aggregated confederata only 

 in the divisions of the oral retractor and in the position of the first 

 sphincter of the ventral lip, which is just below the second sphincter 

 in contact with the epithelium of its inner surface. The atrial 

 muscles (fig. 131) differ more from those of the aggregated confederata 

 (fig. 125). Each muscle in one is present in the other, but their con- 

 ditions and connections are different. 



The dorsal eye (fig. 132) differs from that of confederata (fig. 126) 

 only in being raised on a stalk of considerable 

 length, formed by the optic nerve, whose fibers 

 in both hicaudata and confederata enter the eye 

 between its two divisions. 



The accessory eyes in the ganglion are simi- 

 lar in the species and in the subspecies. 



With any strictly scientific definition of sp<>- 



Cl.S.3 



a.s.i 



• a.o. 



Fig. 130.— Pegea confederata, 

 subspecies bicaudata, aggre- 

 gated zooid, dorsal view. 

 From Strf.iff (1908). 



Fig. 131.— Pegea confederata, subspecies bicaudata, aggre- 

 gated FORM, ATRIAL MUSCULATURE VIEWED FROM THE LEFT 



side. From Streiff (1908). 



cies, and species among the Salpidae are clearly demarcated and real, 

 one would have to recognize hicaudata as a true species, but the re- 

 semblance to confederata is so close that it is probably preferable to 

 rank bicaudata as a subspecies of confederata. This classification 

 emphasizes the evident close relationship between the two forms. 



Pegea is a highly modified subgenus. It is noteworthy that the 

 solitary form, which in most species is in all respects more con- 

 servative than the aggregated zooid, has, in this species, diverged 

 from the ancient character almost as much as the aggregated zooids. 



