52 



PROTOZOOLOGY 



the contraction of the myonemes. All observers agree that the 

 myoneme is a highly contractile organella. 



Many stalked peritrichous ciliates have well-developed myo- 

 nemes not only in the body proper, but also in the stalk. Koltzoff's 

 studies show that the stalk is a pseudochitinous tube, enclosing 

 an inner tube filled with granulated thecoplasm, surrounding a 



cl 



m 



mc 



m 



bg 



gis 



Fig. 14. Myonemes in Stentor coeruleus (Schroder), a, cross-section 

 of ectoplasm; b, surface view of three myonemes; c, two isolated 

 myonemes; bg, basal granules; cl, cilium; gis, granules between striae; 

 m, myonemes; mc, myoneme canal. 



central rod, composed of kinoplasm, on the surface of which are 

 arranged skeletal fibrils (Fig. 15). The contraction of the stalk 

 is brought about by the action of kinoplasm and walls, while 

 elastic rods will lead to extension of the stalk. Myonemes present 

 in the cihates aid in the contraction of body, but those which 

 occur in many Gregarinida aid apparently in locomotion, being 

 arranged longitudinally, transversely and probably spirally (Fig. 

 15). In certain Radiolaria, such as Acanthometron elasticum 



