236 CILIATE FIBRILLAR SYSTEMS 



are probably associated with the longitudinal rows of cilia running paral- 

 lel to the contractile fibrils (Fig. 83). 



Methods 



Fixative: Schaudinn's. 



Stains: Iron-haematoxylin, acid borax carmine. 



Entodiscus borealis (Powers, 1933). — The following distinct groups 

 of fibrils and associated structures characterize the fibrillar system of 

 Entodiscus borealis: (1) the stomatostyle, with its dorsal and ventral 

 anterior horns and their adoral fibrils; the labial fibrils; the pharyngeal 

 fibrils; and the circumpbaryngeal rods; (2) the anterior fibrillar center, 

 or motorium, with its anterior, posterior, and marginal strands; the pos- 

 terior auxiliary fibrillar center with its associated strands; and (3) the 

 peripheral transverse commissural fibrils interconnecting the basal gran- 

 ules. Closely associated with the commissural fibrils are the distal branch- 

 ing ends of most of the internal fibrils. The ventral peripheral layer 

 is further complicated by the long (6-12 p) ciliary rootlets, which ex- 

 tend into the endoplasm from the basal granules of the cilia. 



The pellicle of the ventral surface is thicker than elsewhere and is 

 highly difiPerentiated owing to pellicular fibrils accompanying each 

 longitudinal ciliary row. These fibrils are conspicuous only at the anterior 

 end. They are interpreted as either supporting or contractile in nature 

 (Fig. 84). 



Methods 



Fixatives: Schaudinn's, Da Fano's, 2 5 -percent osmic acid, Flemming's 



without acetic acid (the two latter fixatives for sections). 

 Stains: Iron alum haematoxylin, Yabroff's silver method. 



Entorhipidium echini (Lynch, 1929). — One fibrillar system of Etito- 

 rhipidium echini consists of a motorium which is connected to a network 

 of peripheral fibrils linking all the basal granules. The other set of fibrils 

 is developed in the pellicle, chiefly on the ventral surface. 



The motorium is located to the left of the buccal cavity. It is com- 

 posed of five heavy strands united into a rod-like body by longitudinal 

 fibrils which appear to be continuous with the neurofibrils of the basal 

 granules. These delicate longitudinal fibrils unite the basal granules of 

 each peripheral row of cilia, and other fibrils encircle the body, uniting 



