EUPLOTES WORCESTERI: I. 297 



long as itself. When first seen the Euplotes had the anterior end of the 

 Lembns in its pharj'nx. The Lembus was alive and struggling; several 

 times it was forced, along, the pharynx and its tip entered the protoplasm 

 of the Euplotes; once nearly one-half its body was in the endosarc of 

 its captor. However, each time it forced its way back, and finally escaped 

 altogether from the Euplotes and moved awaj^ giving no evidence of 

 ha-^ing received any harm. On another occasion a Euplotes was found in 

 the act of swallowing an amoeba of elongated form. A little less than 

 one-half of the body of the amoeba then lay in the pharynx, completely 

 filling about two-thirds of this organ, and blocking the membranellse 

 - so that none of them could act. As a result, after a few efiiorts the 

 amoeba reversed the direction of its motion and crawled out of the 

 pharynx, across the adoral zone, and away. I have frequently observed 

 that small protozoa and bacteria are thrust into the mouth between the 

 adoral and suboral menibranellEe. and then are pushed along by the 

 pharyngeal membranellai and cilia; currents of water, conveying food 

 particles from the mouth to the tip of the pharyruK, do not appear to 

 exist. A similar conclusion was recently reached by SchafEer regarding 

 the process of swallowing in Stentor. 



The function of the endoral cilia is more difficult to understand than 

 that of the suboral membranellEe, because direct observations are almost 

 impossible. Large food bodies which reach the mouth are grasped easily 

 between the two sets of membranellse. In the case of small particles, 

 like bacteria, the process may be different. Only those which reach the 

 mouth at the level of the tips of the adoral membranellse will be seized in 

 the manner described. Those which lie in a lower, i. e. more ventral, 

 level will pass over the posterior wall of the peristome with the currents 

 of water. Those which arrive at the dorsal part of the oral aperture wUl 

 be brought within reach of the endoral cilia and pushed along to the tip 

 of the pharynx. If the Euplotes lies with its dorsal side up, the par- 

 ticles captured by the endoral cilia may fall out of their reach to the ven- 

 tral side of the pharynx, but there they will be pushed along by the 

 tips of the pharyngeal membranellse. However, if the Euplotes is swim- 

 ming with the ventral side up as is frequently the case, the particles 

 captured by the endoral cilia will be thrust along by them until the inner 

 tip of the pharynx is reached. In addition, the inclined position of the 

 pharyngeal membraneUse is such that, with the animal in this position, 

 any particles which escape from them will drop directly upon the endoral 

 cilia and will also be passed dovm the pharjmx. The pharyngeal 

 apparatus of Euplotes is, therefore, a remarkably efficient one. 



On the other hand, if we view the adoral zone of membranellse as a 

 mechanical food conveyor alone, its efficiency is very low, for the currents 

 produced by it are so strong that nearly every particle drawn into the 

 jDeristome is thrown out again over the posterior border at a high speed. 



