248 CILIATE FIBRILLAR SYSTEMS 



cytoplasm of the protozoan, the stouter of these various fibres may serve in 

 addition some function in the nature of support. 



Methods 



Fixatives: Schaudinn's, Bouin's, Jorgensen's, Van Rath's. 

 Stains: Heidenhain's iron haematoxylin, Regaud's haematoxyhn, Mallory's 

 triple (whole mounts and sections). 



Nyctotherus hylae (Rosenberg, 1937). — A detailed description of the 

 neuromotor system of Nyctotherus hylae is given, including two centers 

 and a group of special fibrils believed to control the reversal of ciliary 

 action. An incomplete account of some of these structures was given by 

 Kirby (1932) for N. sylvestrianus. The movements of N. hylae were 

 studied by cinematographic methods. 



From the main motorium located at the distal end of the cytopharynx 

 arise two sets of unbranching fibrils. One set extends along the anterior 

 border of the pharynx, eventually terminating at the end of the peristome. 

 The other set follows the posterior border and arm of the ectoplasmic 

 thickening. Some of the latter fibrils unite at the cytostomal border with 

 the peripheral peristomal fibril. The so-called "reversal fibrils" originate 

 from the posterior part of the motorium, radiate through the endoplasm, 

 and at their distal ends unite with the ciliary lines at several points, not 

 including the presutural ciliary lines. 



The membranelles have each a basal plate and two rows of basal gran- 

 ules, from which fine fibrils connect with the circumpharyngeal fibrils. 

 The latter become the transverse peristomal fibrils, of which there are at 

 least two for each membranelle of the series. 



A number of fibrils from the motorium directly connect with the 

 anterior neuromotor center. From this structure arise many ciliary lines 

 that connect rows of basal granules. Commissural fbrils between these 

 lines are present only in the apical post-sutural region. The lateral and 

 sagittal sutures which divide the ciliation into definite regions were 

 interpreted as probable conductors between ciliary lines. 



The pharyngeal ter^ninus, a. deeply staining structure, gives rise to a 

 post- pharyngeal bundle of fibrils that have no apparent distal attach- 

 ment. Kirby (1932) described a similar "band formed structure" in 

 N. silvestrianus which may extend beyond the cytopharynx, its course 

 in the endoplasm varying in dififerent individuals. He considers it "ho- 



