32 



J. H. OKTON. 



as though the cilia in this region were lashing away from the groove. 

 The particles falling on to the region between the buccal tentacles and the 

 peri-pharyngeal grooves, however, are washed into these grooves by cilia 

 in a manner samewhat similar to that observed in Amphioxus. 



At. 



OP 



7. — View of one entire zooid of the compound Ascidian, Lejitodinum gelatinosum, 

 to show the currents i^roduced by the cihary mechanism on the gill and the mode 

 of food-collection. 



(Drawn from the living animal seen through the microscope, x about 60.) The 

 large arrows indicate the direction of the main current, and the dotted ones the 

 course of food-particles which have been captured and are being transported to 

 the dorsal lamina. Only the gill slits on the upper surface are shown. 

 A. Ari'ow indicating the direction of the inhalent current produced by the 

 lateral cilia. I.e. 

 Lateral cilia on the sides of the gill slits : these produce the main current 



by lashing from the pharynx towards the atrium. 



Arrows indicating the current passing through the gill slits into the atrium. 



Dotted arrows indicating the paths of the food-particles, as at M, captured 



in mucus and travelling away from the endostyle towards the dorsal 



lamina, DL. 



Dorsal lamina filled with collected food-particles seen through the wall of 



the transparent pharynx. 

 Endostyle. 

 Food-particles embedded in mucus being transported by the frontal cilia 



on the gill towards the dorsal lamina. 

 Pigment spots scattered about the surface of the colony. 

 Common atrium of the colony. 

 Peri-pharyngeal band. 



I.e. 



B. 



C. 



DL. 



En. 

 M. 



P. 



At. 

 P.b. 



When Leptoclinum (Diplosoma) is fed with a large amount of carmine 

 particles the process of feeding occurs extremely rapidly. Within a few 

 seconds from adding particles to the water the dorsal lamina becomes full 

 of the particles embedded in mucus ready to be passed into the oesophagus. 

 Clavellina can be observed through the microscope to feed in the same 

 way, and almost as rapidly as Leptoclinum. Ascidiella and Ciona feed 



