352 



Universitij of California Puhlications. [Zoology 



Figs. 1. 2, 3, 4 show the various positions assumed by this part 

 of the adoral zone. Fig. 1 shows the anterior edge c4osely ap- 

 plied, a position usually assumed at the connneneement of the 

 gliding, later the anterior corner of the left lip raises as in fig. 2, 

 this continues and as the motion increases an arch is formed as 

 shown in fig. 3, through which the water from the buccal funnel 

 escapes. The left lip continues to elevate itself by a twisting of 



Figs. 1, 2, 3, 4. — Positions assumed by the left adoral lip during gliding. 



the whole anterior end until on the left side the buccal funnel is 

 exposed (fig. 4). The animal is now usually traveling in a path 

 which is a circle with the buccal groove facing inward. The 

 body of the animal remains with the ventral surface applied 

 closely to the bottom, except for a film of water sufficient to allow 

 for the play of the cilia. At times, when the animal is making 

 S)nall circles to the left and the left lip is much elevated, the 

 animal turns on its right side, so that the buccal funnel is com- 

 pletely exposed. 



The posterior eud plays an important part in the direction of 

 gliding. The bending of the posterior end towards the left gives 

 to the animal a curvature which is responsible to a large extent 

 for the direction of movement. This end is extremely flexible, a 

 noticeable feature of the backM'ard movement, when it folds 

 under and to the left. It also acts as a rudder for the forward 

 movement, for the path described usually has the same curvature 

 as is shown by the shape of the body. The posterior tij) is more 



