NUCLEI AND KINETIC ELEMENTS 111 



fibers pass to different regions of contractile activity. These fibers 

 are named and interpreted by Sharp as: (1) A circumoesophageal 

 ring strand (c. r. s.) running to a definite ring of substance similar 

 to that of the motorium encircling the gullet (oes. ring), from which 

 other fibers (oes. f.) apparently take their origin and run poste- 

 riorly along the retractile gullet; (2) a dorsal motor strand (d. m.) 

 running to the bases of the adoral membranelles; (3) opercular fibers 

 (op. f.) or a group of fibers running to the operculum (Fig. 2). 



The delicacy of structure and the position of this amazingly com- 

 plex aggregate are sufficient evidence to disprove any hypothesis of 

 a supporting function. Self-perpetuation of the elements by division 

 indicates no relationship to supporting structures such as trichites 

 (oral basket) in the mouth regions of forms belonging to the family 

 Chlamydodontida?. Their position in the cell and the attachments 

 of the several fibrils are arguments against their interpretation as 

 myonemes. 



McDonald (1922) has recently described a somewhat similar 

 neuromotor system in Balantidium coli and B. suis. Here an ante- 

 rior motorium gives rise to (1) a ring-form fil)ril which passes around 

 the adoral cilia region and (2) a similar ring fibril passing around 

 the gullet. Other elements of the system consist of basal granules 

 of the cilia, from which rhizoplasts pass inward to the central region 

 of the cell. At the point where each rhizoplast enters the enrloplasm 

 is a granular thickening from which a radial fibril passes toward 

 the periphery where it ends blindly. 



Evidence in favor of a conductile finiction of such a neuromotor 

 system is furnished by the observations of Yocom (1918) and the 

 micro-dissection experiments of Taylor (1920) on En plates patella. 

 In Euplotida^, apart from the motile organs, contractility is un- 

 known, nevertheless the literature contains many references to 

 myonemes in the several species. Distinct fibrils in these hypo- 

 trichs which Engelmann regarded as nerve-like in function, have 

 been interpreted in the main as supporting or contracting elements 

 (JNIaupas, Biitschli, Schuberg, INIaier, etc.). Prowazek worked them 

 out in some detail in the case of Euplotes harpa and Griffin (1910) 

 in the case of E. worcesteri, both observers regarding them as con- 

 tractile in function. Yocom has studied them more recently in 

 Euplotes patella and a complex system, comparable with that of 

 Diplodinunn ecaudatnm is described. A definitel\' staining bilobed 

 mass of differentiated protoplasm which Yocom identifies as a 

 motorium is situated in the ectoplasm near the right anterior angle 

 of the triangular peristome (Fig. 57, m). 



From one lobe of this mass a set of five prominent longitudinal 

 fibrils which seem to emerge as a single strand, run to the bases of 

 the five anal cirri near the posterior end (a. c.) ; from the other lobe 

 a single fibril passes along the inner margin of the anterior lip and 



