1918] Yocum: The Neuromotor Apparatus of Euplotcs Patella 351 



the exception of a curve over the pharynx is almost in one frontal 

 plane. In its finer structure the macronucleus is composed of approxi- 

 mately twenty-three thousand granules on a fuie linin reticulum. 

 When well stained with haematoxylin the granules, which range in size 

 from one-fourth to one-half micron in diameter, are very distinct, well 

 separated from one another and almost spherical. This granular con- 

 dition is well brought out when stained with iron-alum haematoxylin, 

 but in specimens stained with IMallory's stain the granules are not so 

 distinctly separated and the whole nucleus appears cloudy and rather 

 opaque. At the time of division a very interesting change takes place 

 in the macronucleus, which will be described later. 



Micronucleus. — The micronucleus is a small spherical body from 

 two to three microns in diameter, lying on the anterior left hand side 

 of the animal in an indentation in the macronucleus {mic, fig. A). In 

 specimens well stained with haematoxylin, the micronucleus appears 

 as an almost homogeneous black body. When stained with Mallory's 

 stain it takes the acid fuehsin quite readily and becomes a bright 

 orange red, while the macronucleus takes only the orange color. At 

 the time of division it migrates from its position occupied during the 

 vegetative stage to the left of the macronucleus and there undergoes 

 mitosis. Usually surrounding the micronucleus is an area almost 

 devoid of granules, probably indicating an area of rapid oxidation. 

 This is quite conspicuous at the time of division (pi. 15, fig, 15). 



MOTOE OEGANS AND THE NEUEOMOTOE APPAEATUS 



The term neuromotor apparatus w^as first used by Sharp (1913) in 

 his account of Diplodinimn ecaudatum to designate a central mass or 

 motorium and fibers connecting it with the motor parts of the animal. 

 To this structure he attributed a neuromotor function, due to the fact 

 that it seemed likely that it had to do with coordinating the movements 

 of the membranelles and operculum and with them formed a single 

 integrated mechanism. 



The neuromotor apparatus of Euplotes patella consists of five dis- 

 tinct parts, namely (1) a motorium or center of motor influences, to 

 use the nomenclature employed by Sharp (1913), from which the 

 fibers pass to the motor organs and sensory lip; (2) five heavy longi- 

 tudinal strands comiecting the anal cirri with the inner end of the 

 motorium; (3) a fiber connecting the inner ends of the cytostomal 

 membranelles with the outer end of the motorium; (4) a lattice- work 

 sensory structure of the anterior lip; (5) a system of fibers, dissociated 



