294 



FISHES 



CHAP. 



Another example of these interesting structures occurs in 

 Chanos salmoneus and a few other Clupeidae ^ in the shape of a 

 coiled gill-like organ (" gill-helix "), which is supported by the 

 dorsal segment of the fourth branchial arch, and enclosed in a 

 similarly curved caecal extension of the branchial cavity. Each 

 gill derives its blood from the fourth afferent branchial artery, 

 the corresponding efferent vessel joining the fourth efferent 

 branchial artery. A similar spirally-coiled " gill-helix " is found 



Fil;. 171. — Accessory respiratory organ of Clarias, as seen after the removal of the left 

 operculum, a, Anterior arborescent organ ; 5.a^"^, the ^rst foTir branchial arches 

 and their holobranchs ; dM.c^ dorsal extension of the left branchial cavity ; /, 

 modified gill - filaments ; op, base of the operculum ; p, posterior arborescent 



also in Heterotis ehrenbergii^ amongst the Osteoglossidae, and in 

 several species of Characinidae.^ 



In other Teleosts the accessory breathing organ assumes the 

 condition of paired lung-like outgrowths of the branchial cavity. 

 Thus, in one of the Symbranchidae, the Indian " Cuchia Eel " 

 {Amphipnous cuchia),^ there is a pair of small bladder-like sacs, 

 with membranous and vascular walls, each of which opens into 

 the branchial cavity above the first gill-cleft, and is supplied 

 with blood by the afferent branchial artery of the gill-less first 

 branchial arch. An extreme modification in the same direction 



^ Hyrtl, Denksch. k. Akad. JViss. Wien. xxiii. 1863, p. i. ; ibid. x. 1855, p. 48. 

 2 Hyrtl, Hid. viii. 1854, p. 185. 



^ Hyrtl, ibid. xxi. 1863, p. 7 ; Sagemchl, Morph. Jahrb. xii. 1887, p. 307. 

 * Taylor, Edin. Joxirn. Sci. v. 1831, p. 33 ; Hyrtl, Denksch. k. Akad. Wiss. 

 Wien. xiv. 1858, p. 39. 



