8 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



by Apstein (1894, b), and C. bakeri, described by Ritter (1905). Cy- 

 closalpa virgula is the sole representative of still a third division of 

 the subgenus. Ritter 's (1906, b) Cyclosalpa retracta, of which only 

 the solitary form is known, seems very similar to Apstein's (1904 

 Salpa amboinensis, and with this species and with S. picteti of Apstein 

 (1904) and S. hexagona of Quoy and Gaimard (1824) it forms a nat- 

 ural group intermediate in some respects between the Cyclosalpas 

 and those Salpidae which have the gut compacted into a so-called 

 "nucleus." This group I am naming Ritteria after Professor Ritter, 

 who described the species retracta. 1 



The three species punctata, asymmetrica, and magalhanica, which 

 I have named Apsteinia, after Apstein, who first described two of 

 this group, 2 agree with the Ritterias, so far as known, and with 

 Cyclosalpa baJceri, C. virgula, and Brooksia rostrata in the asymmetry 

 of their muscles in the aggregated forms, all but Apsteinia punctata 

 showing also asymmetry in the shape of the body. Asymmetry is 

 somewhat less marked in the higher members of the family, espe- 

 cially in Thalia, Thetys, Pegea, and Traustedtia. 



The Cyclosalpas may be divided into two groups — the symmetrical 

 forms, Symmetricdles, including C. pinnata, C. affinis, and C. fiori- 

 dana, and the Asymmetricales, including C. bakeri and C. virgula. 

 The asymmetry characterizes only the aggregated forms of these 

 species and may be related to the manner of their arrangement upon 

 the stolon. Well-developed stolons of C. virgula or C. bakeri have 

 not been described. For C. bakeri, neither Ritter's (1905) descrip- 

 tion nor our specimens show any indication of the formation of 

 whorls, though one of our stolons is very old with the zooids appar- 

 ently ready to drop off. Ritter writes: "As to the whorls of zooids, 

 it can only be said at present that the close similarity of this species 

 to Cyclosalpa affinis and C. pinnata in the arrangement of the zooids 

 in the chain makes it highly probable that the whorls are likewise 

 much the same in the two." In the Albatross Philippines collec- 

 tions were three individuals of the aggregated form of this species 

 which were 12 mm. in length, three times as long as Ritter's and our 

 specimens from the California coast. These three delicate collapsed 

 individuals are united together, but not in any way indicative of 

 either the presence or absence of whorl formation. The three sym- 

 metrical species of Cyclosalpa are well known to form distal whorls 

 upon their stolons. We have no evidence that the Cyclosalpas with 

 asymmetrical aggregated individuals do form such whorls, and one 

 suspects that they do not and that the asymmetry of their aggregated 

 individuals is correlated with the conditions of crowding in a biseri;il 

 stolon. 



i Ritter, 1906,6. 



'Apstein (1894, 7>, and 1901). 



J Of course pseudobiserial; really a uuiserial chain with alternate liuks crowded out to opposite sides. 



