20 



General Morphology of the Protozoa 



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Fig. 1. 11. A. Longitudinal fibril joining basal gianules in Entorhi- 

 pidiiim echini; longitudinal section of cortex; xl890 (after Lynch). B. Trans- 

 verse connecting fibrils in E. echini; cross-section of cortex; xl800 (after 

 Lynch). C. Frayed cirrus of Oxytricha fallax showing component cilia; x2025 

 (after Lund). D. cirrus of O. fallax; xl725 (after Lund). E. A membra- 

 nelle of Spiiostomum anihiguimj; diagrammatic (after Bishop). F. Basal 

 granules and connecting fibrils in Tillina canalifera; diagrammatic (after 

 Turner). G. Dorso-ventral fibrils joining basal granules in Opalina obtri- 

 gonoidea; longitudinal section; xllOO (after Cosgrove). Kev: b, basal fibril; 

 c, cilium; e, end-thread; es, endoplasmic spherule; j, longitudinal fibril; g, 

 basal granule; gi, primary basal gianule; gs, secondary basal granule; I, 

 basal lamella; m, membranelle; p, basal plate; t, transverse fibril; tr, tricho- 

 cyst. 



FIBRILLAR SYSTEMS 



The basal granules in each longitudinal row of cilia are joined by 

 a fibril. Transverse fibrils may also link the basal granules in some species 

 (Fig. 1. 11, A, B). Tillina canalifera (123) is unusual in that longitudinal 

 and transverse fibrils join secondary basal granules, which in turn are 

 connected by rhizoplasts to superficial primary basal granules from which 

 the cilia arise (Fig. 1. 11, F). In Opali?ia obtrigorioidea, oblique fibrils 

 join basal granules in different longitudinal rows but longitudinal fibrils 

 cannot be detected (34). This situation suggests possible modification of 

 the primitive symmetr)' during the evolution of opalinid ciliates. 



The longitudinal fibrils in certain ciliates seem to be morphologically 

 independent (29). In other species, the fibrils are joined in complex 



