Oh. XXI.] COMPOUND SALP^, 309 



was in every respect precisely like the other, and each con- 

 sisted of a tough bag of transparent jelly, open at each end, 

 through which the water freely flowed. The apertures were 

 large and gaping, and opened alternately, admittiug and ex- 

 pelling the water — the opening at the upper end of the 

 animal, which admitted the water, being of a distinctly 

 valvular character. In nearly every one of these animals I 

 found a small crustacean (Hyperia), which swam freely 

 about in the cavity of their body, and seemed perfectly at 

 home there — ^not probably taken as a prey, but a voluntary 

 tenant, which could swim in and out of the Salpa at pleasure. 

 Few Salpee were without one of these, which was distinctly 

 visible through the transparent walls of the bodj' — so trans- 

 parent that when placed in a white dish the whole animal 

 became invisible, but for the three coloured structures 

 which they aU contained. 



Besides the single Salpae I have mentioned, and which 

 were evidently fragments of a compound animal, there was 

 also a kind differing considerably from them, yet having 

 a family likeness, and which Vogt considers the simple 

 form of Salpa pinnata. It was very rare compared with 

 the compound form, of a fish-like aspect, transparent, open 

 at both ends, with apertures similar in form to the other, 

 but with no process for joining on to other individuals. 

 On each side of the body was a row of beautiful crimson 

 linear bodies, occupjdng rather more than the middle third 

 of the margin ; and its anatomical details, readily observed 

 through its glass-like waUs, were very beautiful. I only 

 managed to secure one of them, though the others were 

 floating by in myriads. 



Associated with the compound Salpse were others of a 

 smaller size, but in every other respect closely resembling 



