26 J. H. OETON. 



this region, and become drawn against the wall of this cavity bv the 

 sets of cilia which are known collectively as the wheel organ. These sets 

 of cilia are shown on the wall of the buccal cavity in Fig. 5. They are 

 really ciliated grooves running antero-posteriorly in the posterior part 

 of the buccal cavity. Around the mouth these paths are connected 

 together by a circular ciliated path, which is stated by V. Wijhe (4) to be 



Fig. 5. — View of the anterior end of a living Amphioxus (drawn as seen through a mici'o- 

 scope, X ca. 27), after keeping the animal in a dilute solution of methylene 

 blue in water. This view shows the action of the buccal tentacles in sieving ofif 

 the coarser food-particles at the entrance to the buccal cavity, the action of 

 the ciliated grooves (the Wheel Organ) in the wall of the buccal cavity, and the 

 collection of food-particles from this region of the body into the peri-pharyngeal 

 bands. 



b.c. Buccal cavity. 



hp. gr. Dorsal or hyperpharyngeal groove, 

 p.b. Peri-pharyngeal band, 

 v.t. Velar tentacles. 

 EN. Region of the endostyle. 



The arrows in the buccal cavity lie alongside the ciliated grooves, along which 

 food-particles are lashed towards the mouth in the direction indicated by the 

 arrows. The large arrow passing through the mouth from the buccal cavity into 

 the pharynx indicates the course of the main stream. 



sometimes complete and sometimes incomplete. These ciliated paths 

 have been said to be " an organ for creating currents in the mouth back 

 to the pharynx." There can be little doubt about their function, however, 

 if they are watched while the animal is feeding. As particles drop out of 

 the main current in the buccal cavity they very quickly become caught 

 in the anterior end of one or other of these ciliated paths and rapidly 

 whirled along the groove towards the mouth, becoming rolled into a 



