96 University of California Publications in Zoology [Vol. \?, 



i.e., 35?5 C, an individual of the species D. ecaudatiim could easily 

 travel a distance equal to twenty times its own length in less than 

 one second. It must be admitted that no accurate measurements were 

 taken, but the most careful and conservative estimates led to the above 

 conclusion. In fact we are convinced that this species holds the speed 

 record for the genus Diplodinium and probably for all of the genera 

 described thus far from the stomachs of ruminants. The normal 

 course taken by a member of this species is not in a straight line, but, 

 like so many of the asymmetrical protozoans, it advances in a right 

 spiral as does the point of a corkscrew when penetrating a cork. This 

 fact becomes doubly interesting when we consider the build of the 

 anterior extremity of the body. We noted imder the description of 

 the organs of nutrition that, owing to the greater thickness and greater 

 height of the adoral membranelle zone and oral disk on the right and 

 dorsal sides of the mouth than on the left and ventral sides, the plane 

 of the mouth was directed toward the left and ventrally. Thus we 

 see that by the clockwise rotation and the spiral course of the body 

 the mouth opening is brought into contact with a greater amount of 

 the surrounding medium and more directly than could possibly be 

 accomplished in any other manner of locomotion. Keeping in mind 

 that all the evidence points toward a bacterial diet for this species, 

 and therefore the probable necessity of great numbers of these small 

 food particles, we are struck with the wonderful co-ordination of 

 locomotor and nutritive organs, which makes for efficiency in food 

 getting. 



Another interesting fact was one day forcibl.y brought to my 

 attention when, after returning to the laboratory with samples from 

 the contents of ten stomachs, I was absolutely unable to find a single 

 member of the species D. ecaudatiim. As all of these samples had 

 been taken from the same herd of cattle, the question arose, Does 

 geographical environment play any part in infecting cattle with this 

 protozoan? Careful records kept from that time on have furnished 

 the following information: (1) In the same herd some cattle may be 

 heavily infected with ciliated protozoans, others very slightly. (2) In 

 the same herd some cattle may be heavily infected with some or all 

 of the species of one genus and not with another, while other cattle 

 reverse the conditions and contain heavy infections of those species 

 and genera which the first cattle lacked. (3) In the same herd some 

 cattle contain only certain forms of a species, while other cattle contain 

 only other forms of the same species. (4) In the case of Diplodinium 



