lOG 



BIOLOGY OF THE PROTOZOA 



viduals of Zoothamnium arlmscida contracts instantly into a minute 

 ball. These varied movements which are quite independent of 

 movements of translation or rotation, are due to the contraction 

 of specialized muscle-like fibrils, the myonemes. These are long, 



Fig. 55. 



-Epistijlis Tplicatilis; longitudinal section showing myonemes {MY) from 

 membranelles to base of cell. (After Schroder.) 



delicate, contractile threads, circular or band-like in cross-section 

 situated in the cortical zone and running throughout the entire 

 length of the body either straight (Stentor) or spirally (Sinro- 

 stomvm). In some cases a second set of myonemes run transversely 

 about the body as in the peristomial regions of Canipanclla vinheUaria 



