3322. But, at the same time that the trachea is inserted within the mouth, it opens externally and in the lateral direction upon the body, thus letting the water escape from it posteriorly after a mussel-like or sexual fashion. Thus, the trachea is not yet closed inferiorly, nor hence also the thoracic cavity. Between the head and abdomen there are still openings—branchial foramina.
3323. The trachea is itself, however, a thorax upon a small scale, consisting as it does of rings, or as it were ribs. These arches are not yet united by muscles with each other, and the water flows out between them into the apparent thoracic cavity, from which it next escapes beneath the branchial operculum.
3324. These tracheal rings are the branchial arches. The branchial vessels are tracheal and by no means pulmonary vessels.
3325. Thus, upon taking a retrospective glance at the matter, we may fairly conclude that the branchiæ of the Dermatozoa are not equivalent to the lungs of the higher animals, but are only the antetypes of the bronchi, being thus cervical organs.
3326. The trachea is thus formed prior or antecedently to the lungs, but is still membranous and devoid of any continuous connexion between its rings.
3327. The lung is an organ extraneous or foreign to the trachea, and becomes only as if accidentally associated with it.
3328. But a Sarcozoon is not devoid of lungs nor of aerial respiration; for, being the totality of all lower animals, it consequently unites in itself the respiratory apparatus of the Branchial and Tracheal animals; thus gills and lungs.
3329. In the Fish the first lung appears, that is to say, if we designate or interpret the respiratory organ in Insects only as tracheæ, which do not open into the mouth.
3330. The Fish's lung is the air-or swim-cyst.
3331. The lung is still subordinate to the abdomen and intestine. It is therefore still separated from the trachea or the branchial arches.