350 University of California Publications in Zoology [Vol. 18 



any other of the intravitim stains gave satisfactory results. However, 

 by studying animals which had become quiet under the cover glass, it 

 has been determined that under normal feeding conditions there is a 

 definite cyclosis of the cytoplasm in the area anterior to the anal cirri 

 and to the right of the cytostome. This movement of the cytoplasm 

 is in an anti-clockwise direction and may carry the food forward 

 almost to the region of the motorium. There seems to be no evidence 

 that the food of Euplotes follows the curve of the macronucleus as 

 Greenwood (1894) has described for Carchesium. Powdered carmine 

 was also put in the medium but from the very few cases in which any 

 of it had been ingested by the Euplotes, it would seem that Euplotes 

 patella exercises some choice in food. This is in accord with Griffin 

 (1910) who found that E. ivorcesteri also did not ingest powdered 

 carmine. No definite attempt has been made to determine the process 

 of digestion in E. patella, but it would seem from the use of intravitam 

 stains to determine the path of the food vacuoles that it would be 

 more difficult to determine the digestive processes in the Hypotricha 

 than it is in forms like Paramoecium and Carchesium. 



CONTRACTILE VACUOLE 



There is but one contractile vacuole. At the time of its greatest 

 distention it is from twenty-five to thirty microns in diameter and lies 

 anterior to the two outer anal cirri and wathin two or three microns of 

 the right hand edge of the bodj^ Its period of pulsation is relatively 

 slow. In normal animals which are at rest the interval is seventy to 

 seventy-five seconds, while in animals slowed down by the use of 

 nicotine the vacuoles may pulsate only once in three to four minutes. 



NUCLEAR STRUCTURE 



Macronucleus. — As in the case with most ciliates, Euplotes patella 

 is binucleate with large macronucleus and small micronucleus. The 

 macronucleus is rodlike and bent in the shape of a C wdth the two 

 ends on the right side of the body {mac, fig. A). The macronucleus 

 lies in the endoplasm and there is no indication that it is surrounded 

 by ectoplasm in a manner described for Diplodinium by Sharp (1913). 

 Due to its large size it is by far the most conspicuous structure in the 

 organism. Its length is about two hundred and thirty microns, and its 

 width, eight microns. It lies about midway dorsoventrally and with 



