352 University of California Publications in Zoology [Vol. 18 



from the above mentioned parts of the neuromotor apparatus, radiat- 

 ing from the nine cirri on the right ventral field and the four posterior 

 marginal cirri. 



In the following description the term neuromotor apparatus will be 

 used in the same sense as it was used by Sharp (1913) in his account 

 of Diplodinium ecaudatum, that is as a primitive nervous system over 

 which sensory and motor impulses may pass, for coordinating the 

 movements of the motor parts of the animal. It may be that in such 

 forms as the Protozoa we have a condition too primitive to allow of 

 attributing a purely nervous function to this system, and that in the 

 evolution of the ciliates the functions of conductivity and contractility 

 have not become entirely separated. However, in the following discus- 

 sion it is our purpose to show that in Euplotes patella there is a 

 system which is a primitive nervous system structurally united with 

 the motor organs, and evidence will be brought forth to support such 

 a contention. Nevertheless it must be understood that in considering 

 this as a primitive nervous system we are considering it as a system 

 in which the sensory and motor functions are not entirely separated, 

 and that, with the exception of the structure in the anterior lip, all 

 fibers and granules are probably endowed with the function of trans- 

 mitting both sensory and motor impulses. 



Structure of Cirn. — Before taking up a description of this neuro- 

 motor apparatus it is necessary to devote some space to a description 

 of the minute structure of the motor parts of the organism. These 

 motor organs are of two kinds, the cirri and membranelles, structures 

 quite different in appearance but essentially alike in the structure and 

 functioning of their elemental parts. 



Little, if anything can be added to the descriptions already given 

 of the structure of cirri as Maier (1903) has fully taken up the struc- 

 ture of these organs in ciliates in general and has brought together the 

 principal facts concerning these organelles. Griffin (1910) has dis- 

 cussed the cirri of one species of Euplotes. The cirri of E. patella 

 conform to the general descriptions given, but do not agree in at least 

 one point with that for E. ivorcesteri (Griffin, 1910). This will be 

 taken up in a discussion of the basal granules of the cirri. 



The cirri of Euplotes may be divided into three groups according to 

 their size. The largest cirri are the five anal cirri which extend from 

 the ends of the five longitudinal grooves posteriorly over the margin 

 of the body. These cirri lash back and forth in one plane. The next 

 smaller in size are the nine cirri anterior to the anal cirri. These lash 



