298 GRIFFIN. 



A \-ery low ijercentage of particles is thrown into the angle where the 

 mouth is located and large numbers of these eventualh^ are lost. How- 

 ever, the ad oral zone is more than a food conveyor, it is also the principal 

 organ of locomotion ; a balance of functions exists such that an increase 

 of efficiency in either direction without other modifications would be 

 fatal. 



This Euplotes appears to be selective in its feeding, if tests made with 

 carmine are of any value, for I have seen but one specimen which 

 swallowed any carmine granules, and that one took only a few. While 

 bacteria were being swallowed in large numbers, the carmine grains were 

 swept out of the peristome as if the animal were unconscious of their 

 existence. The experiment has been repeated several times and some 

 hundreds of Euplotes observed. It is noticeable also, that when several 

 kinds of food are present in an infusion one kind appears to be preferred, 

 as is proved by the nature of the food masses in the Ijodies of the in- 

 fusorians. 



Minute food particles are collected in the form of a dense ball at the 

 iianer end of the pharynx before being swallowed, as in many other 

 infusorians. Boom for this is provided, not in the pharynx itself, but in 

 an evagination of the anterior side, projecting into the endosarc, and 

 increasing in size as the food mass gi'ows. Text figure 5 shows an early 

 stage of the evagination, and a later stage is represented in Plate V, 

 figure 10. When the l^all is finally ingested no visiljle layer of water 

 accompanies it. 



Membmnellce. — The number of adoral membranellse varies between -±5 

 and 70. The anterior ones are strikingly long. (Plate I, figure 1.) 

 Passing toward the mouth, a gradual reduction in length occurs so that 

 near and at the mouth they are al^le to swing freely within the edges of 

 that opening. 



Minkiewicz describes the adoral membranellas of E. vannus as trian- 

 gular, and Wallengren represents those of E. liarpa as of a similar shape. 

 After repeated' examination I am convinced that the shape of the ex- 

 panded membranella of E. worcesteri is nearly rectangular, about as shown 

 in Plate I, figure 1. However, some are longer on the outer than the 

 innei' side, while very frequently during action the membranellEe assume 

 a triangular shape by the inner side being drawn toward the outer. The 

 membranellas of this genus are extremely flexible organs, showing but little 

 modification from the condition of free cilia. 



The memliranellaj of this species, even in the living condition, do not 

 appear to Ije liomogeneous. As soon as the motion of these organs slows 

 in a captured specimen, each membranella appears to consist of a double 

 row of delicate cilia, closely set, and moving exactly together but without 

 any visible uniting substance. 



After fixation and staining, no matter what the method, the appearance 



