278 University of California* Publications in Zoology [VOL. 20 



the individuality of each basal granule. There is no evidence of fusion 

 of granules, though adjoining granules are connected by a neuromotor 

 fiber. However, in the triangular area mentioned above, there is con- 

 siderable evidence that the cilia are united to form membranelles. It 

 is very difficult to watch the action of these cilia, and the above con- 

 clusion was reached largely through a study of fixed material. In 

 cross-sections (pi. 27, fig. 4) the cilia of the region seem to be very 

 close together and quite regularly to be connected by, or to form, a 

 sheet of almost transparent substance. The regularity of this occur- 

 rence would lead one to believe that it is the normal structure and not 

 due to entanglement of the cilia in foreign matter. In addition, the 

 basal granules of this region (pi. 27, figs. 4 and 5) do not stand out 

 separately, but are so closely packed that they give the appearance 

 of a single deeply stained mass. I have been unable to distinguish 

 separate granules in the inner portion of the area and it seems likely 

 that actual fusion of the granules may have occurred. The basal 

 apparatus of this region is so densely packed and takes stain so readily 

 that in certain views it may easily be mistaken for the motorium. As 

 a result, it seems plausible to interpret this area as the basal apparatus 

 of membranelles which lie in a plane transverse to the axis of the 

 oesophagus. If this region be interpreted as a primitive oral groove 

 or cytostome, a forerunner of such an elaborate arrangement as occurs 

 in Euplotes patella (Yocum, 1918) or in Stentor, then comparison is 

 very significant, for in the latter two the membranelles also run trans- 

 versely in the cytostome. The only difference, then, between these 

 organisms and Balantidium in this regard would be the difference in 

 shape and extent of the area. 



The adoral cilia (ad. til., fig. I) are approximately double the 

 length of the body cilia, i.e., from 6/x to S/A in length or, in the very 

 large individuals, they may reach a maximum length of 10/x. In 

 fundamental structure they are like the body cilia, but the relative 

 position of parts is somewhat different. Immediately beneath the 

 pellicle each cilium bears a basal granule and from this a fiber con- 

 tinues inward which passes between the adoral plug and the surround- 

 ing ectoplasm. The sum of all the fibers from adoral cilia marks off 

 very distinctly the conical cytostomal region from the surrounding 

 ectoplasm. They seem to constitute the only partition between the 

 protoplasm of the two areas, for I have not been able to detect any 

 membrane in this region making a complete separation of the adoral 

 region from the rest of the apical cone. Where the fibers pass from 



