CILIARY MECHANISMS ON THE GILL IN AMPHIOXUS. 



23 



bars is very easily seen even in a view like that of Fig. 3, and if the lateral, 

 i.e. the anterior and posterior, faces of the gill-bars be focussed carefully, 

 rows of long, rapidly moving cilia are to be seen lashing across the length 

 of the bars. In Fig. 4 this direction is indicated by the large arrows. 

 In a view of a portion of the pharynx, as shown in Fig. 3, these lateral 

 cilia — as thev mav be called — lash in the direction shown bv the arrows 



ENDOSTYLE 

 Fig. 3. — View of a portion of the pharynx of Amphioxus to show the cilia producing the 

 main current (on the left) and the collection and transportation of food -particles 

 (on the right). The portion consists of a piece of the endostyle with gill-bars 

 attached. (Drawn from the living object, x ca. 32.) 



The arrows on the reader's left indicate the direction in which the main current 

 is drawn by the lateral cilia on the gill-bars. These cilia are shown bordering the 

 gill-slits. The arrows on the reader's right show the direction in which the frontal 

 or pharyngeal cilia on the gill-bars are transporting a mass of food-particles away 

 from the endostyle towards the dorsal groove. The upper arrow on the right- 

 hand side of the figure points to the food-mass. The small arrows in the middle 

 of the figure on the endostyle show the direction in which the outer, i.e. lateral 

 cilia, on the endostyle transport particles out of the endostylar groove on to the 

 gill-bars. The supporting rods of only a few of the gill-bars are shown. 



on the reader's left-hand side, and thus draw water with suspended 

 particles against the side of the gill. Water is actually lashed between 

 the gill-bars, as is indicated by the lower arrow on the extreme left of this 

 figure, while the suspended particles are caught in mucus on the face of 

 the gill-bars, and, as we have already seen, are carried away from the en- 

 dostyle towards the dorsal groove (see Fig. 3 again on the right). In the 



