The same type of branchial organs persists in _Chondropterygians_, which possess five, rarely six or seven, flattened pouches with transversely plaited walls. The septa between them are supported by cartilaginous filaments rising from the hyoidean and branchial arches. Each pouch opens by a cleft outwards, and by an aperture into the pharynx, without intervening ducts. The anterior wall of the first pouch is supported by the hyoidean arch. Between the posterior wall of the first and the anterior of the second sac, and between the adjacent walls of the succeeding, a branchial arch with its two series of radiating cartilaginous filaments is interposed. Consequently the first and last pouch have one set of gill-laminæ only, viz. the first on its posterior and the last on its anterior wall. The so-called _spiracles_ on the upper surface of the head of Chondropterygians are to be referred to in connection with the respiratory organs. They are the external openings of a canal leading on each side into the pharynx, and situated generally close to and behind the orbit. They frequently possess valves or an irregularly indented margin, and are found in all species during the embryonic stage, but remaining persistent in a part only. The spiracles are the remains of the first visceral cleft of the embryo, and in the fœtal state long branchial filaments have been observed to protrude, as from the other branchial clefts. The _Holocephali_ and _Ganoidei_ show numerous deviations from the Chondropterygian type, all leading in the direction towards the Teleosteans. As a whole they take an intermediate position between the preceding types and the Teleosteans, but they show a great variation among themselves, and have in common only the imperfect separation of the branchial sacs and the presence of a single outer branchial aperture. In _Chimæra_ the septum separating the branchial sacs is confluent with the wall of the gill-cavity in a part of its extent only, and still more imperfect is the separation of those branchial divisions in _Ceratodus_ (Fig. 60). The other Ganoids show no such division whatever. In _Chimæra_ the first gill is incomplete (uniserial), and belongs to the hyoid; then follow three complete gills; the last, belonging to the fourth branchial arch, being again incomplete. _Acipenser_, _Scaphirhynchus_, _Lepidosiren_, _Protopterus_, and _Lepidosteus_, possess likewise an anterior incomplete gill (_opercular gill_), followed by four complete gills in the Sturgeons and _Lepidosteus_, whilst in _Lepidosiren_ and _Protopterus_ a part of the branchial arches is gill-less. In _Polyodon_, _Ceratodus_, and _Polypterus_, an opercular gill is absent, the two former having four complete gills, the latter three and a half only. _Spiracles_ are still in some Ganoids present, viz. in the Sturgeons and _Polypterus_. In all the Ganoids an osseous gill-cover is now developed.