292 University of California Publications in Zoology [VOL. 20 



each other and with the motorium. The cilia of the apical cone are 

 connected with the adoral cilia by the radial fibers and so indirectly 

 with the motorium. In this case, however, coordination with the adoral 

 cilia is most essential and this corresponds with their intimate con- 

 nection. These morphological interrelations all point to a neural func- 

 tion for the neuromotor apparatus. 



Very convincing experimental evidence of the neural function is 

 to be found in the results of Taylor's (1920) microdissection experi- 

 ments on Euplotes patella. In Euplotes there is a fiber connecting the 

 adoral membranelles with the motorium, and also a fiber connecting 

 each of the five anal cirri with it. In a series of experiments Taylor 

 severed various ones of these fibers and observed very carefully the 

 effect on the movements of the animal. He then compared these move- 

 ments with the normal movements which he had previously carefully 

 analyzed and classified. Severing of these fibers resulted in lack of 

 coordination of the parts thus disconnected and resulted in abnormal 

 movements. Incision made in other parts of the cell, but which did 

 not sever neuromotor fibers did not so result. In the words of the 

 author, "It is apparent, then, that the destruction of the motorium 

 or the severing of some or all of its attached fibers is alone accountable 

 for modification in the perfect and efficient coordination between the 

 series of membranelles and the anal cirri. We may, therefore, regard 

 these normal morphological relationships as conditioning the animal's 

 usual behavior both in creeping and in swimming." 



The general occurrence among Protozoa of protoplasmic modifica- 

 tion to form organelles for locomotion, feeding, digestion, excretion, 

 and protection has been known almost as long as have the Protozoa 

 themselves. The functions of such organelles have not been difficult 

 to determine. One might equally well expect to find modifications 

 correlated with the conduction of stimuli, but the establishing of 

 neural function is not so easy. This difficulty in conjunction with the 

 traditional idea of the simplicity of the Protozoa has resulted in con- 

 servatism in crediting any intracellular structures with the function 

 of conductivity. The recent detailed morphological studies on Proto- 

 zoa and the experimental work of Taylor (1920), however, leave little 

 doubt regarding the matter. This account of the neuromotor appa- 

 ratus of Balantidium coU and Balantidium suis presents additional 

 evidence of the likelihood of a quite general occurrence, in the Pro- 

 tozoa, of intracytoplasmic specialization resulting in a more or less 

 integrated system for purposes of coordination. 



