698 CLASS xi. 



Ann. des Sc. not., $i&me Serie, vi. 1846, Zoologie, pp. no 131. HUXLEY 

 Observations upon the Anatomy and Physiology of Salpa and Pyrosoma. Phil. 

 Trans. 1851, Pt. II. p. 567. 



The species of Salpce are very generally dispersed ; sometimes 

 they are met with in incredible quantities together j notwithstand- 

 ing, these animals a century ago were entirely unknown. The first 

 announcement of them was made by P. BROWN in his Civil and 

 Natural History of Jamaica, published in 1756, under the name of 

 Thalia; afterwards followed the description of the species observed 

 in the Mediterranean and Red Sea, under that of Salpa by the 

 Danish traveller FORSKAL'. Bosc and CUVIER next pointed out 

 the resemblance of these animal species, described under two differ- 

 ent names, which ought to be referred to the self-same genus. 



The body has an aperture at each extremity, but these apertures 

 have a different form. The one is broad and transverse, and presents 

 a valvular membrane, inasmuch as one of its margins is reflected 

 inwards. The valvular membrane prevents the efflux of the water, 

 which flows inwards by this opening and which is expelled by the 

 opposite one from the contraction of the body. This expulsion of the 

 water is the means by which the animal moves, so that the narrower 

 opening is turned backwards. CUVIER thought that this opening 

 was the anterior, and that thus the animal moved backwards. 

 Since, however, the stream of water conducts also the food, and 

 since in the Ascidice the entrance to the oesophagus is situated 

 behind in the respiratory sac, the common opinion, that the broad 

 opening is the anterior, deserves to be preferred to this idea. The 

 intestinal canal is situated on the outside of the respiratory cavity, 

 in the space intervening between the external and internal covering, 

 but terminates by both its apertures in the respiratory cavity. 



These animals, according to the testimony of PERON, TILESIUS, 

 MEYEST and others, are usually phosphorescent by night. The Salpce 

 are met with at one time singly, as distinct individuals, at another, 

 united either in rings or in long chains, of which the arrangement 

 is various, yet similar in individuals of one and the same species. 

 These are attached to each other by tubercles or prolongations. 

 CHAMISSO, from his observations on living animals, arrived at 

 the conclusion, that successively a generation of distinct Salpce 

 alternates with that of Salpce connected, and forming a chain. 

 Thus a metamorphosis occurs, which, however, does not take place 



1 BRUGUIKRE, who gave in the Encycl. method, an extract from the descriptions of 

 FORSK., changed the name Salpa into Biphora, which has found no general acceptance. 



