182 ELECTRON-MICROSCOPIC STRUCTURE OF PROTOZOA 



threadlike filaments with a diameter of 5 m/x. The polygonal 

 meshwork was called the infraciliary lattice system by Sedar and 

 Porter, after a pattern discovered in the same position by the light 

 microscopist, G. von Gelei (see Parducz, 1958a). 



Ehret and Powers (1957, 1959) have devoted considerable 

 attention to the fine structure of the buccal cavity of "Paramecium 

 bursaria. They were able to show, in confirmation of earlier 

 light-microscope work, that the buccal apparatus includes three 

 long columns of cilia, with four rows of regularly close-packed 

 cilia in each column, and a non-ciliated ribbed wall. In the ciliated 

 columns, one parasomal sac is present for each four cilia, and 

 fibers identified as kinetodesmal (but looking rather filamentous 

 in the published print) run beneath rather than beside the crowded 

 kinetosomes. The ribbed wall is heavily ridged and underlain by 

 fibrous structures of uncertain arrangement. 



The morphology of discharged trichocysts of Paramecium was 

 described in Chapter 2. The undischarged trichocyst consists of 

 an elliptical or carrot-shaped body of rather low density, sur- 

 rounded by a membrane. This is surmounted by a bullet- shaped, 

 heavy- walled cap that is pressed against the outer pellicle membrane 

 between alveoli. Within the cap is a slender dense rod that 

 becomes the pointed tip of the discharged trichocyst. In dividing 

 cells, fibrous elements are distinguishable in the dense walls of 

 trichocyst caps cut in cross section. The fibers, according to Ehret 

 and Powers, resemble the axial fibrils of the cilium, but their 

 outlines seemed considerably less clear and accurate counts of 

 their number were not possible. Trichocysts in at least some 

 ciliates are derived from kinetosomes, according to LworT(1950). 

 Additional observation on their development and fine structure 

 is needed. 



The cytoplasmic matrix in Paramecium (Fig. 75, PL XX) is 

 rather densely packed with Palade granules, meandering double 

 membranes or vesicles, both smooth and granular, and mito- 

 chondria of conventional microtubular structure — but no Golgi 

 bodies have been reported. In addition several peculiar details 

 have been described. Schneider (1959, 1960a, 1960b) illustrates 

 tubular structures, sometimes in rather loosely parallel tracts and 

 sometimes very precisely packed ; these he finds only in the region 

 of the complex contractile vacuole, described in Chapter 2. 



