50 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



are asymmetrical, and that among Cyclosalpas only species which are 

 not known to form whorls on the stolon show this asymmetry. 



We can say that there is one type of muscular arrangement under- 

 lying the somewhat divergent conditions in the solitary forms of the 

 whole subgenus Cyclosdlpa, and another equally well-marked type 

 underlying the various conditions seen in the aggregated zooids of 

 all species of the subgenus. The evidence from the muscles points 

 to the acceptance of the subgenus as a natural one. This conception 

 of natural relationship is strongly borne out by the conditions in the 

 eyes, in the outgrowths from the ganglion, and in the neural glands. 



The gut is similar in position and structure in the solitary forms 

 of all the species, except that in Cyclosdlpa floridana the caeca are 

 small and in C. affinis one is missing. The solitary Cyclosalpas are 

 the only Salpidae which have the gut lying along the dorsal side of the 

 gill. In the aggregated zooids, on the other hand, we find the more 

 aberrant species of the subgenus approaching the true Salpae, the 

 gut becoming bent into a loop, which however is not, in any species, 

 compacted into what could be called a "nucleus." 



Similarly, in the aggregated forms, the large eye of the asym- 

 metrical species approaches the condition seen in Ritteria, Apsteinia, 

 and the true Salpae. 



Brooksia, new subgenus. 



BROOKSIA ROSTRATA (Traustedt 1893). 



Salpa roslrata Traustedt, 1893. 



This subgenus I name after Prof. W. K. Brooks, who has so ex- 

 haustively studied the Cyclosalpas and whose studies of other mem- 

 bers of the Salpidae have been extensive. Its only species, rostrata, 

 resembles Cyclosdlpa virgula, but differs from this species in having 

 the gut, iri both solitary and aggregated forms, in the shape of a rather 

 close loop, much as is the case in the Ritterias. I have no specimens 

 of this subgenus. 



BROOKSIA ROSTRATA, solitary form. 



This has been studied by Traustedt (1893), Apstein (1894, b), and 

 Ihlo (1910). The shape of the body is very peculiar for a solitary 

 Salpa (figs. 22, and 23, p. 51). It has a great antero-ventral protu- 

 berance from below the mouth, equal in length to the whole of the 

 rest of the body. In the aggregated zooids of Salpa maxima, S. fusi- 

 formis and S. cylindrica we find similar processes. They contain no 

 musculature, but at least in some specimens, especially of S. cylindria, 

 one finds connective tissue fibers running lengthwise in the anterior 

 protuberance. At the base of the protuberance they are continuous on 

 oach side with the ventral end of the intermediate muscle. These 

 fibers in the anterior protuberance in the Salpae might function in 



