548 BIOLOGY. 



trachea having taken place with the oesophagus or the 

 mouth. 



3322. But, at the same time that the trachea is in- 

 serted 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 branchiae 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 antece- 

 dently 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 tracheae, which do not open into the 

 mouth. 



3330. The Fish's lung is the air- or swim-bladder. 



