56 



BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



I 



Little can be said of the oral and atrial muscles except that, as figured 

 by Apstein, there are three sphincters in the upper lip and that Ihle 

 mentions the presence of an oral retractor stretching back to the first 

 body muscle. 



Ihle's figure (1910, fig. 16, pi. 1) of the gut (our fig. 28) shows 

 conditions exactly paralleling what Ritter (1906, b) shows for Ritteria 

 retracta, except that the caecum is apparently not flattened, as Rit- 

 ter shows it for R. retracta. Apstein's best figure of the gut (1904, 

 fig. 13, pi. 12), though not his description, while less clear, agrees 

 with Ihle's description. 



Ritter found in Ritteria retracta a problematic organ ("x") protrud- 

 ing on the left side of the body from near the junction of esophagus, 



intestine, and caecum (fig. 25 B, q, p. 54). 

 He says: "A delicate strand seems to pass 

 off from near its tip [base] toward the intes- 

 tine." Apstein (1904 and 1906, a) shows 

 ■ for Ritteria picteti a probably similar crgan, 

 which he calls a glandular appendix of the 

 1 intestine (fig. 27, q). Ihle finds a shorter, 

 stockier body in a similar position, calling it a 

 blood-forming organ (fig. 28, q). Its nature 

 and function are in doubt, but its presence 

 emphasizes the close resemblance between 

 Ritteria picteti and R. retracta. This mass of 

 cells, of problematic function, in these two 

 species, is probably homologous with the 

 more or less well-developed masses or groups 

 no. 28.-ritteria picteti, soli- of ' ' eleoblast-like " l cells we have described 

 tart form, ventral view of ■ thi f several species of Cyclosalpa 



POSTERIOR END. X 2 DIAMETERS. r f • r 



from ihle (1910). (pi. 10, fig. 25, q; pi. 13, fig. 33, tip of caecum). 



The function and interpretation of these cells can not well be discussed 

 without knowing their embryonic origin. 



The only noteworthy differences between Ritteria picteti and R. 

 retracta, so far as our knowledge of them goes, are the larger number 

 of body muscles in R. picteti and the interruption of all of them on 

 the ventral side. These features, especially the latter, leave no 

 doubt of the distinctness of the species. 



The aggregated form of Ritteria picteti is unknown. 



RITTERIA AMBOINENSI9 (Apstein, 1904). 



Salpa amboinensis Apstein, 1904, not 1906, b. 

 S. amboinensis Ihle, 1910. 

 Apstein (1904) and Ihle (1910) have studied this species. I have 

 had 11 specimens of the solitary form, but no well-grown aggregated 



> This resemblance to eleoblast tissuo is in histological appearance only. It is not intended to suggest 

 that there is any homology with eleoblast cells. 



oe: 



anr~-\- t 



