. On the anatomy of vertebrates. Vertebrates; Anatomy, Comparative; 1866. GILLS OF FISHES. 316 tlic bvancliial stream by an orifice, h, near the middle line of the ventral surface: between the two outlets of these lateral longi- tudinal canals, but nearer the left one, is a third larger opening, /, which communicates by a short duct with the end of the long ttsophagus, I, and admits the water, which passes from that tube by the lateral orifices,y, leading into the branchial sacs. This is the first step in devclopcment beyond that simjiler condition which prevails in the Lancelot, where the who
. On the anatomy of vertebrates. Vertebrates; Anatomy, Comparative; 1866. GILLS OF FISHES. 316 tlic bvancliial stream by an orifice, h, near the middle line of the ventral surface: between the two outlets of these lateral longi- tudinal canals, but nearer the left one, is a third larger opening, /, which communicates by a short duct with the end of the long ttsophagus, I, and admits the water, which passes from that tube by the lateral orifices,y, leading into the branchial sacs. This is the first step in devclopcment beyond that simjiler condition which prevails in the Lancelot, where the whole parietes of a much dilated (xsojihagus, fig. 169, rr, are organised for res}>iration ; and besides the pharyngeal ojiening, ph, the sac communicates by a short and wide ' ductus cesophago-critaneus,' ib. od, with the external surface, and also with the peritoneal cavity. The common resjnratory surface of the (lesophagus is ciliated in the Lancclct. The sacs developed from the oesophagus, and specially set apart for respiration in the Myxinoids, have a highly vascidar, but not a ciliated mucous surface : this is disposed in radiated folds, and is further increased by secondary plicjc. The seven branchial sacs on each side of the oesophagus have short external ducts, fig. 313, /(, which open by as many distinct orifices in the skin in a species of Bdellostoma hence called liep- tatreuta: the internal branchial ducts com- municate by as many openings, ib. /, witli the oesophagus. In the Lampreys there are, also, seven stigmata on each side ; but another stage in the separation of the respiratory from the digestive tract is here seen, for each in- ternal duct communicates with a median canal, fig. 310, d, beneath and distinct from the oesophagus, terminating in a blind end behind, and communicating anteriorly with the fauces by an opening guarded l^y a double membranous valve. In all higher fishes the inlets to the branchial interspaces are situated on each side the fauces, a
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Keywords: ., bookauthorowenrichard18041892, bookcentury1800, bookdecade1860
