1918] Yocum: The Neuromotor Apparatus of Eiiplotes Patella 355 



will be called the motorium, a term employed by Sharp (1913) in his 

 paper on Diplodinium ecaudatum to indicate a "common center of 

 motor influences," and it is in this sense that the term will be used 

 in this paper. 



The motorium as indicated above is slightly narrower at its middle 

 part than at the two ends, is about eight microns long and lies in a 

 frontal plane and obliquely to the median longitudinal axis of the 

 body (mot., fig. A). It was first seen as a dark body in the animals 

 stained with iron-alum haematin, lying close to the right anterior 

 corner of the triangular cytostome. In specimens which are well 

 destained this body is seen to be composed of very fine granules closely 

 grouped together, but if too dark it has the appearance of an almost 

 homogeneous body. When stained with Mallory's stain the motorium 

 becomes bright red from the acid fuchsin and lacks the granular 

 appearance characteristic of specimens colored with haematin. Plate 

 14, figure 5 (mot.) shows that this motor mass does not have a smooth 

 contour, but rather that it has ragged edges with processes extending 

 out into the surrounding ectoplasm. 



Joining to the left end of the motorium are the five large main 

 longitudinal fibers from the five anal cirri (a.c.f., fig. A). These 

 fibers converge to such an extent that they appear to join the motorium 

 as a single strand. By careful examination under high magnification, 

 these five fibers are seen to be composed of fine granules arranged so 

 closely together that the fibers have the appearance of granular cords. 

 This granular condition is evident only in specimens stained with 

 haematin. After such treatment the fibers are very conspicuous, 

 darkly stained cords lying close under the pellicle of the ventral side. 

 When stained with Mallory's connective-tissue stain these fibers take 

 the acid fuchsin and become bright red. 



A careful study has been made to determine how these fibers join 

 the anal cirri, but so far the results have not been entirely satisfactory. 

 In a few cases the appearance has suggested that at the anterior edge 

 of the cirrus the fiber begins to break up into a fan shaped structure 

 of fine fibrils which join the basal granules of the cirrus (pi. 14, fig. 6). 

 This point is very difficult to determine, for as was suggested in the 

 description of the cirri, the basal plate of the cirrus is dense and 

 opaque, and if it is sufficiently destained to become transparent enough 

 to study, the fibers lo.se all of their color and become indistinguishable. 

 Sections have failed to lend any evidence in favor of this, and the only 

 evidence gained has been from a few well destained whole mounts. 



