CILIATE FIBRILLAR SYSTEMS 193 



elles, such as the fibrillar system, and to condense that review within 

 reasonable bounds, the difficulties soon become evident. For this reason 

 it has seemed advisable in the review that follows, in the interests of 

 students and laity as well as of specialists, to present a fairly detailed 

 account of the structural analysis, together with interpretations of the 

 fibrillar differentiations of a well-known representative of each of four 

 major groups of ciliates. This is followed by a brief review of other 

 published work, mostly since 1920, on fibrillar systems in other ciliates, 

 with some suitable illustrations; and finally, a few paragraphs of general 

 discussion are added under the caption "Conclusions." 



The discussion of the structural analysis of the fibrillar systems of the 

 four representative ciliates, Paramecium, Stentor, Euplotes and Vorti- 

 cella, is off^ered first and separate from the interpretations for these four 

 ciliates, whose order is then, for convenience, reversed. This separate 

 treatment was decided upon primarily for the sake of accuracy and clarity. 

 Often in the literature the author's interpretations are so intermixed with 

 his factual descriptions that it is sometimes very difficult to make certain 

 just what he observed and undertook to describe. 



Examples of Fibrillar Systems 



a. structural analysis 



1. Paramecium. — This familiar representative of the holotrichs has 

 doubtless been more generally used in both teaching and research labora- 

 tories than has any other of the numerous kinds of ciliates. Probably 

 its apparent simplicity, more than its smaller size, tended to discourage 

 a search for a fibrillar system, such as had been found in Stentor and 

 other forms. 



In 1905, however, Schuberg described for both Paramecium and 

 Prontonia fibrillar diff^erentiations which, running close under the pel- 

 licle, united the basal granules in the longitudinal rows of cilia. By 

 means of a bichromate-osmic fixative and Loeffler's stain, not only was 

 this relationship of fibril and basal granules clearly defined, but also, 

 because of their staining properties, they could be well differentiated 

 from the hexagonal, or rhomboidal, pattern of the pellicle, as was well 

 illustrated in Schuberg's several figures. 



In 1925, J. von Gelei described in Paramecium nephridiatum a periph- 

 eral network of fibrils which was not connected with the familar po- 



