284 University of California Publications in Zoology [ V L. 20 



NEUROMOTOR APPARATUS 



The term neuromotor apparatus denotes an integrated system of 

 fibers, with a coordinating center, which is present in some Protozoa, 

 and which is credited with the power of conductivity of nervous im- 

 pulses, and hence functions in the coordination of the motor organelles 

 of the cell. The term was first used for ciliates by Sharp (1914) in 

 his account of the structure of Diplodiniwm ccaudatum. Since then 

 it has been employed by Kofoid and Christiansen (1915), Kofoid 

 (1916) for flagellates, and by Yocom (1918) and by Taylor (1920) 

 in their studies of the morphology and behavior of Euplotes patella. 



The neuromotor apparatus of Balantidium coli can scarcely be 

 considered apart from the motor organelles of the cell. To insure 

 clarity in the description and discussion which follows, the motor 

 organelles, previously described in some detail, will be briefly reviewed. 

 With the exception of the oral plug which surrounds the cytostome 

 the organism is thickly beset with cilia. Of these, the adoral cilia are 

 largest. They are distributed about the margin of the peristome in 

 a row which ends in the membranellar region in the ventral wall of 

 the oesophagus. The rootlets of these cilia are exceedingly long, reach- 

 ing well into the posterior third of the cell, where they end without 

 any connection or attachment. They have two enlargements, the first 

 being the basal granule which lies just beneath the pellicle, and the 

 second being located at the junction of ectoplasm and endoplasm. 

 The remainder of the cilia are arranged in longitudinal spiral rows. 

 The most anterior cilia of these rows, i.e., those nearest the adoral 

 cilia, are nearly as sturdy as the adoral cilia themselves. But, pro- 

 gressing -posteriorly in the rows, the cilia become continuously smaller 

 until they reach their minimum size at the base of the apical cone of 

 ectoplasm. Likewise the ciliary rootlets become shorter, and the dis- 

 tance between the basal granules and the secondary enlargements of 

 the rootlets becomes less and less as one approaches the base of the 

 apical cone. This is shown in figure I. The remainder of the way 

 posteriorly the cilia are of uniform size, and the secondary enlarge- 

 ment of the basal apparatus of each cilium is the termination of the 

 ciliary rootlet and lies in the granular band of ectoplasm near its 

 plane of junction with the endoplasm. 



In Bala/ntidium coli five distinct parts constitute the complete 

 neuromotor apparatus, namely (1) a motorium or coordinating cen- 

 ter, embedded in the ectoplasm close by the oesophagus, and from it 

 fibers pass out to the oral plug and the motor organelles ; (2) a circum- 



