186 ELECTRON-MICROSCOPIC STRUCTURE OF PROTOZOA 



composed of similar longitudinal fibrils, extend into the core of 

 the tentacle. The core in the non-feeding ciliates examined appears 

 to be occupied by undifferentiated cytoplasm. 



Prehensile tentacles of Ephelota are band-shaped, up to 10 ^ in 

 width, and taper to a pointed tip; they are capable of slow 

 movements of flexion and contraction. Their pellicle and cuticle 

 are like those of sucking tentacles, but here the resemblance ends. 

 Internally the prehensile tentacle is subdivided by septa continuous 

 with the pellicle into five to seven longitudinal compartments. 

 Within each compartment an axial fiber (detectable by light 

 microscopy and protein in nature) consists of a large bundle of 

 very fine (no dimensions given), approximately parallel, longitu- 

 dinal filaments, embedded in a somewhat granular matrix. In 

 cross-section the disposition of fibrils within the bundle is seen 

 to be irregular, enclosing empty spaces in a sponge-like mass. The 

 bundles extend well into the cell body where they are surrounded 

 by endoplasm. 



The very differently arranged fibrillar structures in the two types 

 of suctorian tentacles invite speculation, but this is better deferred 

 until we have examined fibrous structures in additional ciliates. 

 That suction operates in suctorian feeding is indisputable 

 (Kitching, 1954) but its nature remains unknown. Peristaltic 

 waves of contraction in feeding tentacles have been described, but 

 some authors consider these insufficient to account for the flow 

 of food. Kitching has noted a wrinkling of the cuticle over the 

 cell body following capture of prey and suggests an expansion of 

 the body surface with resulting negative internal pressure. If the 

 cuticle resisted inward collapse, suction via the tentacles would 

 result. Unfortunately, no published electron-microscope studies 

 have included detailed observations on feeding animals. 



Within the suctorian body, the food is enclosed in vacuoles, 

 according to Rudzinska and Porter (1954b). Rudzinska (1958) 

 found the surface of Tokophrya to be limited by two membranes 

 separated by a narrow space. In some of her micrographs the 

 outer one seems to be double, but whether this is comparable 

 with the pellicle of tetrahymenids is not evident. A zone of 

 homogeneous, moderately dense material appears outside of the 

 membranes, but nothing comparable to the alveolar layer of 

 Ephelota is seen. A silverline system is present in both adults and 



