56 



PROTOZOOLOGY 



in the ectoplasm. In well-studied ciliates, there occurs a fine fibril, 

 kinetodesma (Chatton and Lwoff, 1935), a short distance to the right 

 of the kinetosome (Fig. 23). The ciliary row or kinety (Chatton and 

 Lwoff) consists of the kinetosomes and kinetodesma (Fig. 23, a). In 

 forms such as Suctoria in which cilia occur only in the swimming 

 stage, the kinetosomes appear to be present as infraciliature (Chat- 

 ton, Lwoff and Lwoff, 1929). 



Flagellum 



Undulating 

 membrane 



Nucl( 



Blepharoplast 



Fig. 9. A diagram showing the structure of a trypanosome (Ktihn). 



As to its structure, a cilium appears to be made up of an axoneme 

 and contractile sheath (Fig. 10, a). Gelei observed in flagella and 

 cilia, lipoid substance in granular or rod-like forms which differed 

 even among different individuals of the same species; and Klein 

 (1929) found in many cilia of Colpidium colpoda, an argentophilous 

 substance in granular form much resembling the lipoid structure of 

 Gelei and called them "cross striation" of the contractile component 

 (Fig. 10, b, c). In electron micrographs of a dried cilium of Para- 

 mecium, Jakus and Hall (1946) found that it consisted of a bundle of 

 about 11 fibrils extending the full length (Fig. 10, d). These fibrils 

 were about 300-500 A in diameter. As there was no visible sheath, 

 the two observers remarked that if a sheath exists, it must be very 

 fragile and easily ruptured. 



The cilia are often present more densely in a certain area than 

 in other parts of body and, consequently, such an area stands out 

 conspicuously, and is sometimes referred to as a ciliary field. If this 

 area is in the form of a zone, it may be called a ciliary zone. Some 

 authors use pectinellae for short longitudinal rows or transverse 



