CILIATES 177 



tiny finger-like diverticulum, the parasomal sac. In all three 

 tetrahymenids studied, the central fibrils of the cilium originate 

 in a small dense granule above the kinetosome. Within the latter, 

 an axial rod of dense material appears, ending just short of the 

 kinetosome's apex. 



Metz and Westfall (1 954) were able to isolate the buccal apparatus 

 from sonicated Tetrahymena and showed that it consisted of the 

 closely aligned kinetosomes of the three membranelles and 

 undulating membrane, all connected to a fan-shaped array of 

 substantial fibers apparently outlining the buccal cavity but 

 extending beyond the mouth deep into the cytoplasm. Observa- 

 tions on the buccal apparatus in sectioned Tetrahymena are not 

 available. In Colpidium and Glaucoma, one wall of the buccal cavity 

 bears conspicuous ridges, and filaments that do not appear tubular 

 in the material studied interconnect buccal kinetosomes and form 

 a mat along one side of the cavity. 



In this connection it may be mentioned that there is some 

 question whether the fibers of the buccal cavity of Tetrahymena 

 are trichites comparable to those in the pharyngeal region of 

 gymnostomes (see below). Present evidence suggests that they 

 are not. However in Frontonia, another hymenostome, Rouiller, 

 Faure-Fremiet, and Gauchery (1956d) have found true trichites 

 composed of subfibrils packed in orderly arrays. 



The observations of Elliott and Tremor (1958) on conjugant 

 pairs of Tetrahymena pyriformis show an extremely close apposition 

 of pellicles in the contact zone. Apparently the outer pellicular 

 membrane, underlain by a dense cytoplasmic layer, is the only 

 one present here, the alveoli having disappeared. The apposed 

 pellicles are interrupted at frequent intervals by pores through 

 which cytoplasmic continuity between mates is established. No 

 bilia or kinetosomes are observed in the area of contact. 



Relatively little attention has been given to the internal fine 

 structure of tetrahymenids. In their comparison of dividing 

 -nicronucleate and amicronucleate strains of T. pyriformis, Roth 

 and Minick (1961) found a decrease in the compactness of intra- 

 mitochondrial tubules, frequently accompanied by the appearance 

 of an amorphous central inclusion, during early division stages 

 of amicronucleate cells. At the same time, granular cytoplasmic 

 membranes increased in quantity and sometimes formed compact, 



