178 ELECTRON-MICROSCOPIC STRUCTURE OF PROTOZOA 



convoluted masses. These authors' observations on nuclear 

 structure have been recorded in Chapter 2. 



In Pitelka's studies of the three tetrahymenid genera (1961a), a 

 layer of homogeneous dense material, varying in thickness, was 

 commonly observed immediately beneath the innermost pellicle 

 membrane. Endoplasmic reticulum frequently parallels this layer, 

 and may appear as rather extensive lamellae elsewhere, often 

 surrounding mitochondria. Some of these membranes have 

 granular outer surfaces, and Palade particles may be very abundant 

 in the cytoplasmic matrix. Mitochondria are distributed through- 

 out the cell but are particularly common peripherally, where they 

 may form compact rows between meridians. Mucigenic bodies 

 are diffuse, low-density, pear-shaped structures with their narrow 

 ends pressed against the outer pellicular membrane along the 

 meridians; occasionally the outer membrane appears to be 

 ruptured, resulting in an open pore. Curved piles of membranous 

 discs identifiable as Golgi bodies are seen only occasionally. 



In the course of their study of mucigenic bodies of the tetra- 

 hymenid, Ophryoglena mucifera, Grasse and Mugard (1961) observed 

 pellicular alveoli presumably identical with those described here, 

 although they recognized only two of the three membranes in 

 the pellicle. A longitudinal fibril band was also seen. 



The most detailed accounts of the ultrastructure of Paramecium, 

 based on sectioned material of high quality, have been published 

 by Sedar and Porter (1955), Schneider (1959, 1960a, 1960b), and 

 Ehret and Powers (1959 and earlier papers cited there). An early 

 study of fragmented cells by Metz, Pitelka, and Westfall (1953) 

 provided basic information on pellicular and fibrillar patterns, 

 while various other aspects of Paramecium ultrastructure have 

 been considered by Bretschneider (1950), Tsujita, Watanabe, and 

 Tsuda (1954, 1957), Potts and Tomlin (1955), Wohlfarth- 

 Bottermann(1956, 1958a, 1958b), Blanckart(1957), Dippell(1958), 

 Hamilton and Gettner (1958), and Roth (1958a, 1958b). Valuable 

 analytical reviews of light- and electron-microscope data are 

 provided by Ehret and Powers (1959) and by Parducz (1958a). 



The polygonal sculpturing of the surface of Paramecium is 

 familiar to every protozoologist; this pattern appears clearly in 

 silver-stained specimens, which also show argentophilic lines 

 along the kineties. The ultrastructural basis of this silver line 



