1918] Yocuni: The Neuromotor Apparatus of Euplotes Patella 349 



the granules do not show but in their places are vacuole-like structures, 

 the granules apparently being dissolved out by the action of the 

 killing fluids. The rosette arrangement of the granules was best shown 

 in specimens stained with neutral red, killed by osmic acid fumes and 

 studied in the unpreserved condition. Posteriorly the rows of granules 

 extend to the margin of the body but anteriorly they end about ten 

 to fifteen microns from the anterior membranelles. There is no evi- 

 dence that these rosettes center around the bases of sensory bristles in 

 Euplotes patella as Griffin (1910) indicated for E. ivorcesteri. 



ENDOPLASM 



The endoplasm {end., pi. 14, fig. 5) occupies the central portion of 

 the animal and lies just beneath the ectoplasm, but ventrally it is 

 separated from the pellicle by only an extremely thin layer of the 

 ectoplasm. The endoplasm is alveolar in structure and contains large 

 granules, but these are not so numerous as in the ectoplasm. AVith 

 Mallory's stain the central part of the cell stains pink. In this endo- 

 plasm are embedded the nuclei, food vacuoles and undigested food. 

 It seems that the fibers from the cirri are also in this layer, but 

 although this is the case it is undoubtedly true that they have arisen 

 in the ectoplasm and have sunk into the lower layer. 



FOOD VACUOLES 



The food of Euplotes consists of bacteria, small flagellates, ciliates 

 and diatoms, which are wafted into the pharynx by the constant action 

 of the membranelles. Under what might be called normal feeding con- 

 ditions, the ingested food lies enclosed within the area surrounded by 

 the macronucleus and most of it lies in the space to the right of the 

 cytostome and anterior to the anal cirri. At times when food is very 

 abundant, Euplotes feeds voraciously and as a result the whole body 

 becomes gorged with engulfed organisms. At such times the area in 

 which the food vacuoles are normally located becomes greatly enlarged 

 and extends forward as far as the motorium and laterally and pos- 

 teriorly as far as the narrowing endoplasm permits. Under these con- 

 ditions the structure of Euplotes is very difficult to study as the 

 ingested food stains heavily and obscures the true body structures. 



Several attempts have been made to determine the path of the food 

 vacuoles, but neither congo red, as used by Metalnikow (1912), nor 



