66 STRUCTURE 



body of each component cilium gives rise to about 10 fibrils which 

 run down into the cytoplasm for about 20 fi (Fig. 15). These 

 fibrils are regularly arranged in a hexagonal array with transverse 

 interconnecting filaments about 60 A thick which give a very 

 solid structure. The fibrils from each membranelle converge into 

 a tight bundle which bifurcates at the inner end to join similar 

 branches from the two adjacent membranelles ; the roots of all 

 the membranelles are thus joined together at their inner ends. 

 Another " thick strand of fibrous material " was found by Randall 

 and Jackson (1958) joining the roots of all membranelles near the 

 body surface, but unfortunately we do not know any details of 

 this structure. All the information that we have about the function 

 of these deep roots points to the fact that they serve to anchor the 

 bases of the membranelles of Stentor. 



A hexagonal pattern of rather similar appearance is made by 

 rootlet connections in the infundibular region of the peritrich 

 Campanella (Rouiller and Faure-Fremiet, 1957), although in this 

 case the structure seems to be a three-dimensional array, rather 

 than an array of longitudinal fibrils transversely connected by 

 filaments. The cilia are arranged in tw^o triple rows, and the inner 

 ends of the basal bodies give rise to groups of 2 or 3 fine filaments 

 (10 to 20 A in diameter) which diverge and join with those from 

 other ciliary bases, interconnecting to form a hexagonal pattern 

 with granular nodes at the junctions. Sections in several planes 

 give a similar appearance. In the peritrich Carchestum^ the bases 

 of the cilia in each peristome row are linked together by fibrils 

 200 A thick (Randall, 1956). 



The roots of membranelles of Nyctotherus (King, Beams, 

 Tahmisian and Devine, 1961) and the '' retrociliary fibrils " which 

 form the roots of membranelles in the Ophryoscolecidae (Noirot- 

 Timothee, 1958), seem to be composed of bundles of fibrils 

 similar to those forming the roots of Stentor membranelles, 

 though perhaps lacking the terminal connexions betw^een adjacent 

 roots and the cross-filaments between adjacent fibrils. In EuploteSy 

 roots of this type have not been described, but both membranelles 

 and cirri have well-developed root systems whose rootlets run 

 parallel to the body surface. Roth (1956, 1957, 1958a, 1958b) has 

 described these rootlets, which are bundles of apparently tubular 

 fibrils about 210 A in diameter, and without cross -striations 



