44 



ZOOLOGY 



SECT. 



entering the pharynx, passing thence by the gill-slits into the atrium, 

 and out at the atriopore. The current, as in Tunicata and Balano- 

 glossus, is both a respiratory and a food current, the animal feeding 

 passively on the minute organisms in the surrounding water. 



FIG. 699. Amphioxus lance Olatus. Diagrammatic transverse section of the pharyn- 

 geal region, passing on the right through a primary, on the left through a secondary branchial 

 lamella. o. dorsal aorta ; e, derm ; ec endostylar portion of coelome ; /. fascia or investing 

 layer of myomere ; fh, compartment containing fin-ray; g. gonad ; gl. glomerulus ; A-, 

 branchial artery ; M, pharynx ; lit, combined atrial and coelomic wall (ligamentum denticu- 

 latum) ; m. myomere ; nit. transverse muscle ; n. nephridium ; of, metapleural lymph-space ; 

 j>, atrium ; sc, co3lome ; */, ventral aorta ; sk, sheath of notochord and neuron ; v.f, spaces in 

 ventral wall. (From Korschelt and Heider, after Boveri and Hatschek.) 



CcBlome. Owing to the immense size of the atrium the body 

 cavity, which is a true coelome, is much reduced. It is represented, 

 in the pharyngeal region, by paired cavities (Fig. 698, cod., Fig. 697, 

 A, co., Fig. 699, sc.) lying one on either side of the dorsal region of 



