1922] McDonald: On Balantidium coli and Balantidium suis 287 



It has not been possible to demonstrate a posterior continuation 

 of the radial fibers within the granular bands. If they do not continue 

 posteriorly, making connections with the enlargements of the rootlets 

 of the body cilia, then the logical alternative seems to be to attribute 

 the function of conductivity to the granular band of ectoplasm itself. 

 There must be some means of conduction of stimuli, for the body cilia 

 are concerted in their action, though not to so high a degree as in 

 the case of the cilia of the apical cone. Protoplasm is generally con- 

 ceded to have the power of conducting stimuli. So here in Balan- 

 tidium coli there seems to be a transition from conduction by the 

 undifferentiated protoplasm which serves as a- matrix for the ciliary 

 apparatus, to a condition in which there is a differentiation of the 

 protoplasm into fibers or strands to serve the purpose. Moreover, the 

 increasing degree of differentiation is directly correlated with the 

 increasingly high degree of coordination of the motor organelles. 



It will be seen from the figures and the above description that 

 Balantidium coli is equipped with a notably integrated system of 

 fibers bearing such morphological relations as would make the assign- 

 ing to them of the function of coordination perfectly logical. The 

 motorium is connected directly only with the oral plug and the adoral 

 cilia. But through ciliary rootlets and the radial fibers all of the 

 cilia of the apical cone are in connection with the adoral cilia. And 

 if the function of conductivity may be attributed to the granular 

 bands of the ectoplasm, into which the radial fibers turn and become 

 lost to view, and in which the enlargements of the ciliary rootlets of 

 the body cilia lie, then all of the motor organelles of the organism are 

 reached by the neuromotor apparatus, and by it the coordination of 

 these organelles may be explained. 



Attributing to the various fibers described above the quality of 

 conductivity and to the whole neuromotor apparatus the function of 

 coordination of all of the locomotor organs in swimming and feeding, 

 microdissection experiments carried on by Taylor (1920), we may 

 consider the functions of the various parts from that point of view. 

 The main role of the motorium is to act as a coordination center. The 

 circumoesophageal fiber would serve to correlate the movements of the 

 oral plug with those of the adoral cilia in feeding and in avoiding- 

 reactions. The ciliary rootlets and radial fibers make possible the 

 coordination of all of the locomotor organs in swimming and feeding, 

 and especially the cilia of the apical cone which are employed in the 

 boring movement of the organism. 



