102 University of California Publications in Zoology [Vol. 13 



the number of valid species in the genus has been reduced from ten 

 to five. 



6. The body is covered by a very resistant cuticle, divided into 

 definite areas, characterized by peculiar surface markings. Three of 

 these areas, because of their relation to underlying skeletal structures, 

 are designated as left, ventral, and right skeletal areas. These three 

 areas with their underlying skeletal structures are separate at the 

 anterior end of the animal, but merge together as they approach the 

 posterior extremity. They afford attachment for the internal retractor 

 structures. 



7. The arrangement of the oral cilia and the adoral membranelles 

 differs from that previously described for this genus. Starting from 

 a point on the left side of the animal, near to the anterior extremity, 

 the adoral row of membranelles circles from left to right around the 

 adoral region until it reaches a point inside of and opposite to that 

 at which it started, then turning upon itself it reverses its direction 

 and now as oral cilia circles from right to left around the oral opening. 



8. There is present in D. ecaudatum, a complicated structure, the 

 neuromotor apparatus, which is probably nervous in function. This 

 apparatus consists of a central motor mass or motorium, from which 

 definite strands radiate: one to the roots of the dorsal membranelles 

 (dorsal motor strand) ; one to the roots of the adoral membranelles 

 (ventral motor strand) ; one to the circumoesophageal ring (circum- 

 oesophageal ring strand) ; and several pass out into the ectoplasm of 

 the operculum (opercular fibers). Each of these strands may send 

 off one or more branches. In the walls of the oesophagus both nervous 

 and contractile fibers may be distinguished. The structural and func- 

 tional relations of these parts are such as to indicate that they con- 

 stitute a neuromotor apparatus. 



The Protozoa have often been defined as simple, one-celled animals. 

 Calkins (1909, p. 1) says of them: "Their beauty, their varied modes 

 of life, the suddenness of their appearance and disappearance, the 

 simplicity of their structure and modes of reproduction combine to 

 make them, even to the superficial observer, a fascinating group." 

 From the present study of these ciliated protozoans of the stomach of 

 the ox we may conclude that in the various forms of the species 

 Diplodinium ecaudatum are to be found some of the most interesting 

 and also the most complex of all known Protozoa. 



Transmitted May 10, 1913. 



