tou2.pt. 2.] A TAXONOMIC STUDY OF THE SALPIDAE METCALF. 127 



them is a mass of pigment cells. 1 Thetys is noteworthy in having 

 abundant pigment associated with the antero-dorsal eye within the 

 ganglion. 



The neural gland in the aggregated zooids of Thetys vagina (fig. 118) 

 is unique. Instead of two disks below the ganglion, each opening 

 by a tube to the peripharyngeal chamber, there is a single huge 

 evagination of this chamber, with a single wide median aperture- 

 The epithelium of that part of the evagination which is in contact 

 with the ganglion is thickened and resembles the dorsal portion of 

 the epithelium of the glandular disks in other species. Remember- 

 ing the origin of the typical disks in other species, as paired evagina- 

 tions from the pharyngeo-cloacal epithelium, it is not so great a 

 divergence from the usual conditions, which Thetys shows. Instead of 

 two evaginations, one right and the other left, Thetys has a single 

 huge median evagination, and this does not develop far enough to 

 close off from the pharyngeo-cloacal chamber. In lasis zonaria 

 there is a single postero-median chamber in the neural gland (fig. 103, 

 p. 108) but this shows paired anterior prolongations. There is also 

 but one duct, but this is lateral, one duct being present and the other 

 absent. [Cf. Salpa cylindrica Metcalf, 1893, c] In Thetys the gland 

 is further modified and it and its single aperture are median. 



Like lasis, the aggregated zooid of Thetys bears several embryos. 



Subgenus Pegea, (Savigne 1816). 



PEGEA CONFEDERATA, (ForskSl 1775). 



Salpa confederata Forskal, 1775. 



S. gibba Bosc, 1802. 



S scutigera Cuvier, 1804. 



S. octophora Cuvier, 1804. 



S. vivipara Peron, 1807. 



Pegea octophora Savigny, 1816. 



Salpa ferruginea Chamisso, 1819. 



S. informis Quoy and Gaimard, 1824. 



Salpa femoralis Quoy and Gaimard, 1826-1834. 



S. quadrata Herdman, 1888. 



I'egea scat%gera-confederala Herdman, 1891. 



S. confederata Apstein, 1894, a. 



In the collections of the United States National Museum there are 

 the following specimens: 



Cat. No. 6433 U.S.N.M. (solitary form), Albatross station D. 4037, 

 Kawaihae Strait, Penguin Bank, south coast Oahu Island, Hawaiian 

 Islands; July 10, 1902; surface; surface temperature 80° F.; 1 

 specimen. 



1 It is noteworthy to find these pigment cells within tho ganglion instead of superficial as in the case 

 of the eyes of the aggregated zooids of all other species. In the eyes of some solitary Salpae, the pigment 

 cells are within the optic ridge, instead of just beneath the epithelium, as in Cyclosalpa pinnata (fig. 4, p. 17). 

 I am unahle to say whether those internal pigment cells are mesodermal, as the superficial pigment cells 

 in tho eyes of aggregated zoiiids seem to be. 



2621— Bull. 100, vol. 2—19 9 



