72 THE VOYAGE OF H.M.S. CHALLENGER. 



body in my specimens do not bulge outwards, as is shown in Traustedt's figure/ but 

 are straight and parallel, and in this respect are more like Traustedt's figures - of the 

 solitary form. 



The Challenger specimen of the aggregated form from Station 320, in the South 

 Atlantic, is precisely like those collected by the " Knight-Errant " in the Xorth 

 Atlantic, and has the pointed posterior end turned very much to the right side. 



One of the specimens from the Straits of Magellan is the largest in the collection. It 

 is nearly 6 cm. in length, and has the posterior projection over 1 cm. in length. In the 

 specimen obtained in the Pacific, on April 3, 1875, the posterior projection is relatively 

 very long, and the muscle bands in the mantle are narrow. In one of the specimens 

 obtained in the North Atlantic, on April 28, 1876, the posterior projection is also very 

 long; while, on the other hand, the specimens from Station 311, in the Straits of 

 Magellan, have their posterior ends very blunt, there being almost no process. The 

 specimen from Station 23G, off the coast of Japan, is rather more slender than usual, 

 and has the posterior projection long and pointed. It measures 7 mm. in length, the 

 length of the whole body being 3 "2 cm. 



The three specimens collected in the South Atlantic, on March 9, 1876, have 

 embryos, occupying the exact position figured by Traustedt. A part of one of these 

 specimens is shown on Plate VII. fig. 5, with three embryos lying between the 5th and 

 6 th muscle bands. Figures 6-9 on Plate VII. illustrate some points in the histology of 

 the aggregated forms collected on March 9, 1876. Figure 6 shows the nervous system, 

 dorsal tubercle, and neighbouring parts. The muscle fibres in these specimens are verj' 

 distinctly nucleated and cross-striated. Figure 7 shows a part of the edge of the dorsal 

 tubercle, and figure 8 some of the ciliated cells more highly magnified. The large 

 nucleated cells forming the lateral appendages of the nerve ganglion are shown in fig. 9. 



The three processes of the mantle, shown running into the test at the anterior end of 

 the body in Traustedt's figure, are not always present in the Challenger specimens. In 

 some there are two processes, in some only one, and in some none of them are present. 



Salpa cylindrica, Cuvier (PL VII. fig. 10). 



Salpa cylindrica, Cuvier, Anu. du Mus., torn. iv. p. 381, 1804. 



lasis cylindrica, Savigny, M(5m., p. 124, 1816. 



Salpa cylindrica, Traustedt, Ivc. cif., p. 277, which see for further sj-nonymy. 



Both solitary and aggregated forms of this species are represented in the Challenger 

 collection. The following is a list of the localities at which the specimens were 

 ■ obtained : — 



(1.) December 27, 1873 ; Station 145a ; lat. 46° 41' 0" S., long. 38° 10' 0" E. ; ofl' 



1 Loc. cit., tab. i. fig. 21. 2 i^g^_ ^n., tab. i. figs. 18 and ly. 



