CILIATE FIBRILLAR SYSTEMS 253 



complex also was found to occur in the caudal spines of D. dentatum, 

 in contrast to the apparently structureless spines in Entodinium. Along 

 the bases of the caudal spines appeared a heavy marginal fibril from 

 which finer anchoring fibrils extended into each spine, terminating under 

 the cuticle of its outer margin. A very heavy main anchoring fibril 

 bordered the inner edge of each spine. From the anchoring fibril of the 

 ventral spine smaller fibrils branched toward the anus, where they ended, 

 one on each side. Small branches from these coursed in the wall of the 

 rectum, parallel to its main axis. 



No connection was evident between this fibrillar complex of the caudal 

 spines of D. dentattwi and its neuromotor system. The location and re- 

 lationships of the former suggested a supporting function similar to that 

 of the longitudinal surface fibrils. Also, since these spines undergo a 

 change in their curvature such as might obviously be facilitated especially 

 by the main anchoring fibril together with the marginal fibrils, these 

 caudal fibrils were considered to be myonemes. 



A similar fibrillar system had been described by Belaf (1925) in 

 Epidinium caudatum, on the basis of which Reichenow (1929) denied a 

 neuromotor function for all fibrils of the Ophryoscolecidae. The clear 

 difference in the morphological relationships of the two fibrillar systems 

 in D. dentatum, however, indicated that these systems have quite difi^er- 

 ent functions: 



The caudal fibrils are admirably situated to serve as supporting and contractile 

 structures. The motor fibrils are so situated as to be of little or no use 

 either as supporting or as contractile fibrils. The caudal fibrils show no con- 

 nection to the motor organelles. The motor fibrils link together (through the 

 neuromotorium) all the motor organelles of the individual. 



Methods 



Fixative: Schaudinn's. 

 Stain: Iron-haematoxylin. 



Favella jorgensen (Campbell, 1927). — The netiromotorium is a 

 spindle-shaped body in the ventral ectoplasmic wall in the mid-region 

 of the gullet. This organelle gives rise to five intracytoplasmic fibrils as 

 follows: ( 1 ) the adoral fibril, extending to and interconnecting the mem- 

 branelles; (2) the circmnesophageal fibril, with branches surrounding 

 the gullet; ( 3) a dorsal fibril which appears to connect with the striations 



