CILIATE FIBRILLAR SYSTEMS 205 



which may appear correspondingly specialized. Another structural dif- 

 ferentiation, the pellicle, assumes in this connection a significant im- 

 portance in maintaining the flattened bodily form so characteristic of 

 the hypotrichs. The often remarkable rigidity of this pellicle has long 

 been recognized. 



Euplotes, the representative whose fibrillar system will now be 

 reviewed, suitably illustrates these well-known characteristics of the 

 hypotrichous ciliates. 



Maupas (1883) was apparently the first to identify fibrillar differ- 

 entiations in this genus. He described in Euplotes patella var. a fibril 

 extending anteriorly from the basal plate of each of the five anal cirri. 

 These five fibrils united into a single fiber, which continued anteriorly 

 and disappeared near the bases of the adoral membranelles. 



Maupas's findings were essentially confirmed by Prowazek (1903) 

 in his brief account of protoplasmic reorganization in E. harpa. He 

 further observed the "solide und fest" nature of fixed anal cirri fibrils, 

 as indicated upon sectioning, when they might be pulled and bent 

 thread-like by the microtome knife. Similar fibrils were seen to extend 

 radially from the bases of the other cirri. Prowazek also described and 

 figured still finer fibrillar lines ("Fibrillenziige") going in parallel to 

 the adoral membranelles. These finer fibrils have apparently not been 

 identified as such by later workers. 



Some years later Griffin (1910) gave a fairly detailed description 

 of the fibrillar system which he discovered in E. worcesteri. From the 

 base of each of its five anal cirri, he observed a fiber extending ante- 

 riorly. All five fibers converged toward the adoral membranelles, near 

 which they disappeared "close to each other." Unlike similar fibers 

 described by Maupas (1883) and by Prowazek (1903) for other species 

 of Euplotes, these of E. worcesteri apparently did not unite to form 

 a common strand and were not traceable to the membranelles. Several 

 finer fibers were found associated with the bases of some of the other 

 cirri. Their number and direction varied, however, and they had no 

 connection with those of the anal cirri. Griffin suggested that all of 

 these fibers might be comparable to myonemes, the number of which 

 had become reduced with a reduction in rows of cilia, as postulated for 

 the hypotrichs generally; but he noted also that some of the fibers may 

 be directed even transverse to the hypothetical original ciliary rows. 



