338 University of California Publications in Zoology [Vol. 18 



PAGE 



Discussion 378 



Fibrillar system in other ciliates 378 



Neuromotor apparatus of flagellates 381 



Homology of neuromotor apparatus in ciliates and flagellates 383 



Summary 386 



Literature cited 388 



Explanation of plates 392 



INTRODUCTION 



In the year 1830 Ehrenberg gave the generic name Euploea to a 

 group of hypotrichous ciliates, but since that name was already used 

 for a group of butterflies he changed the name in 1831 to Euplotes, 

 the name in use today. The same year, 1831, he gave the name 

 Euplotes patella to one of the species in the genus. 0. F. Miiller had 

 described this species as TricJioda in 1773 but in 1786 he changed it to 

 Kerona patella. Later Bory (1824) called the organism Coccudina 

 Jceromina et clausa. In the later works by Stein (1859) and Kent 

 (1881) the generic name remains that given by Ehrenberg (1831). 



The genus Euplotes is distinguished from the other three genera 

 of the family Euplotidae by the presence of four marginal cirri which 

 are entirely isolated from one another; while in Styloplotes, the only 

 other genus having marginal cirri, they are arranged in two fascicles. 



Besides Euplotes patella, the subject of this investigation, there 

 have been described for the genus Euplotes five distinct species. All 

 conform in a general way in shape of body, position of cirri and mem- 

 branelles, and shape and position of nuclei as given below for E. patella. 



Euplotes harpa Stein, the largest member of the group, has a long 

 oval body with broad rounded anterior end. The convex dorsal sur- 

 face is marked by eight longitudinal dorsal ribs. The ventral surface 

 bears ten cirri anterior to the five anal cirri, while the anterior ventral 

 surface carries two blunt denticulations. The posterior margin bears 

 four unbranched cirri. The animal varies in length from 148-180 

 microns. 



Euplotes longipes C. and L. is slightly smaller than E. harpa, being 

 about 138 microns in length, while the ventral surface lacks the 

 denticulations, the whole organism presenting a smooth contour. 



Euplotes cJiaron Ehrbg. is rounded, oval, with the right side feebly 

 but the left side strongly convex. The anterior margin of the anterior 



