338 THE VOYAGE OF H.M.S. CHALLENGES. 



terminal branches, an odd median ampulla and a pair of lateral horns (fig. 1, a). If 

 this explanation be right, Angela would bear the same relation to Epibutia as Canno- 

 physa does to Aurophysa. 



Family XXIV. Physalid^e, Brandt, 1835. 

 Physalidx, Brandt, Prodromus descriptionis, &c, 25, p. 36. 



Definition. — Cystonectas polygastricae with a short inflated trunk of the vesicular 

 siphosome, which is horizontally expanded along the ventral side of the subhorizontal 

 gigantic pneumatophore. Cormidia in a multiple series along the ventral side of the 

 trunk, usually loose. Pneumatosaccus very large, sometimes with a chambered dorsal 

 crest, without radial septa and hypocystic villi. 



The family Physalidaa comprises the largest and most interesting Cystonectae, which 

 surpass all the other Siphonophorae in the enormous size of the inflated pneumatophore 

 and the vigorous tentacles, the splendid colours of the peculiar siphosome, and the 

 dangerous poisons of the urticating organs. Since some forms of this interesting 

 family, and especially the largest of all, the Atlantic Caravella maxima, occur in great 

 swarms floating on the surface of the ocean, they have been well known to travellers and 

 sailors for a long time. In many voyages they are mentioned under the popular names 

 " Caravella, Galera, Fregatta, Ship of Guinea, Portuguese Man-of-War," &c. Never- 

 theless the natural history of the Physalidae has hitherto been very imperfectly studied, 

 and there remains much to be done towards a complete knowledge of them. 



The genus Physalia, generally accepted as the only one of this family, was established 

 in 1816 by Lamarck (90) for those Caravellee which 0. F. Midler and Gmelin in the 

 preceding century had described as Medusa caravella, Linnd, or Holothuria physalis. 

 Neither the name Salacia, employed for them by Linne in a few editions of his 

 Systema naturae (1756, 1, p. 158), nor the name Arethusa, proposed by Patrick 

 Browne in 1789, have yet any application (compare above, p. 330, and below, p. 349). 

 While Lamarck distinguished five different species, with very insufficient definitions, 

 Eschscholtz accepted only three, the common Atlantic Physalia caravella (the largest of 

 all, with numerous large tentacles), the smaller Physalia pelagica (from the Southern 

 Atlantic and Indian Oceans), and the larger Physalia utriculus from the Pacific ; the two 

 latter species have only a single large tentacle, and differ mainly in the form of the 

 pneumatophore. Recently Chun, in the latest paper on Physalia (83, p. 557), unites 

 these two latter forms, accepting two species only of this genus — Physalia caravella, with 

 many large main-tentacles, from the Atlantic, and Physalia utriculus (including Physalia 

 pelagica) from the Indo-Pacific Ocean. All recent authors have accepted the genus 

 Physalia as the only type of this family. 



