28 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



luminous organs are found in the conservative solitary form of several 

 species and in the aggregated form of only one species, we may judge 

 that the possession of luminous organs was an ancestral character 

 which most Salpidae have lost. The presence of luminous organs in 

 Pyrosoma is in line with this suggestion. 



In the solitary Cyclosalpa affinis there are seven hooplike body mus- 

 cles, as in C. pinnata (pi. 3, fig. 9). The intermediate niusclc is 

 interrupted dorsally and complete ventrally {=C. pinnata). The 

 first and second body muscles are interrupted both dorsally and ven- 

 trally ( = C. pinnata) . The rest of the body muscles are all inter- 

 rupted ventrally (=C r . pinnata), but they are continuous dorsally 

 across the mid line. 



The oral retractor muscle is divided horizontally to form two re- 

 tractors, each continued forward into a sphincter muscle of the lower 

 lip. The upper of these two sphincters is admarginal and aids in the 

 incurving of the valve-like lower lip. The more ventral of the two 

 sphincters supports the bulge of the pocket valve which the lower lip 

 forms. There are but two sphincter muscles in the lower lip. The 

 anterior two sphincters of the upper lip are as in the solitary Cyclo- 

 xni pa pinnata. The third and fourth unite at their ventral ends and 

 lie internal to the oral retractors, just in front of the point where the 

 intermediate muscle passes inside them. The third and fourth 

 sphincters of the upper lip are not in actual connection with either the 

 retractors l or the intermediate muscle. 2 As in the solitary C. pinnata. 

 there is in the solitary C ajjinis a longitudinal band of muscle run- 

 ning diagonally upward from the fourth sphincter of the upper lip to 

 the upper end of the intermediate muscle. It does not, however, come 

 into as intimate union with either muscle as in C. pinnata. The atrial 

 sphincters are quite similar to those in the solitary ( '. pinnata, but the 

 atrial retractors are better developed , being connected posteriorly to 

 two rather strong sphincters. 



The gut resembles that of the solitary Cyclosalpa pinnata in posi- 

 tion and form except that there is but one caecum, apparently median. 



The heart lies below the esophagus, in a considerable evagination 

 of the ventral wall of the body. 



Our specimens of the solitary form of this species have the zooids 

 on the stolon but slightly developed and do not show any whorls. 

 Alter Ilitter and Johnson's (1911) careful study of the stolon of this 

 species there is no need of discussion of this structure from our 

 material. 



Tho outline of the aperture of the dorsal tubercle is shown in figure 

 12 of plate 4. 



: In tho solitary Cyclosalpa, pinn ita they connect, with the \ tor. 



- in the aggregated 0. pinmM probably similar muscles connect with the intermediate muscle. 



