THE PELAGIC TUNICATA OF THE GULF STREAM. 



PART II SALPA FLORIDANA (APSTEIN). 



BY WILLIAM KEITH BROOKS. 

 (Plate I, figs, i, 2, 3, 4, 5, 6; plate 2, figs. 7 and 9.) 



This rare Salpa, which is little known, has been noted, by Traustedt, 

 as S. dolichosoma-virgula. (Ergebnisse der Plankton-Expedition der Hum- 

 boldt-Stiftung : Edited by Victor Hensen. II, A. Die Thaliacea der Plank- 

 ton-Expedition : Systematische Bearbeitung; von M. P. A. Traustedt, 1892.) 



It has been more thoroughly described and figured by Apstein, who 

 shows that it is very different from 5\ dolichosoma, and gives it the name 

 S. floridana. (Ergebnisse der Plankton-Expedition der Humboldt-Stiftung: 

 Edited by Victor Hensen. II, B. Die Thaliacea der Plankton-Expedition: 

 Vertheilung der Salpen, von Dr. Carl Apstein, 1894.) 



Apstein gives figures of both the solitary and the aggregated form, but 

 neither stage is drawn from an adult, the figures of the solitary form being 

 drawn from an embryo and those of the aggregated form from a detached 

 member of a young colony. His account contains many minor inaccuracies, 

 as it is based upon these immature specimens, which seem to have been badly 

 preserved and ill-suited for study. 



Mature specimens of both stages were found, in May, 1906, on the sur- 

 face in the vicinity of the Marine Biological Laboratory of the Carnegie 

 Institution of Washington at Tortugas, Florida; and an opportunity was 

 thus afforded to study and sketch them while alive, and thus to make addi- 

 tions to, and some slight corrections of, the account of the species which 

 Apstein gives. 



It is in the shape of the colony of the aggregated form, and in the 

 number and arrangement of its muscles, and those of the solitary form, 

 that my observations are most in conflict with Apstein's account. He says 

 there are ten muscles in the solitary form, while I find no less than sixteen 

 definite and characteristic muscles, without counting the slender ones around 

 the mouth and the cloacal aperture. This discrepancy is due, in part, to 

 the fact that he sometimes regards as one a muscle that is single on one 

 surface of the body, dorsal or ventral as the case may be, when it is repre- 

 sented by two or more on the opposite surface. The hoop-like muscles of 

 Salpa are not like blood-vessels or nerves that have their origin in a central 



NOTE. Professor Brooks's long illness rendered it impossible for him to revise 

 the proof of the following papers, and should any short-comings be discovered in 

 them, such may be attributed to the fact that they have not had the benefit of his 

 personal supervision. 



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