384 University of California Publications in Zoology [Vol.20 



The four flagella stroke from the base with the tip lagging continu- 

 ously through the down and up phase, stopping for an instant in an 

 anterior cluster at the end of the stroke. They pass over the region 

 of the undulating membrane during the stroke. The first effect is a 

 short jerk of the body posteriorly as the stroke begins, followed by 

 a spiral anticlockwise turn of the body in a short arc and a forward 

 thrust. 



It is obvious that only once in its circuit will the independent 

 flagellum pass the clustered flagella. It follows that during the most 

 of the time it is at some distance from the other and if fixed suddenly 

 would, as a rule, lie apart from the four flagella. This we find is its 

 usual position on our stained slides. A knowledge of this fact is of 

 assistance in determining the number of flagella. Failure to observe 

 it may lead to overlooking the fifth flagellum. 



Another characteristic of this and of other trichomonad flagellates, 

 often seen in moribund or slowed-down individuals, is the formation 

 of a stumpj' or finger-like protoplasmic protrusion originating near 

 the anterior end of the body and progressing posteriorly beyond 

 the middle in diminishing prominence. The organism described by 

 Castellani (1905) as Entamoeba undulans is doubtless based on this 

 phenomenon in a moribund trichomonad flagellate. 



The exact nature of this process has not hitherto been determined. 

 Dobell and O'Connor (1921) described it as occurring after "the 

 organism loses its flagella and other organs." As we have observed 

 it, it certainly may occur when all the organelles are present and 

 functioning, though slowly. It is highly probable that it is the mani- 

 festation in slowing-down individuals of the spasmodic contraction 

 or motor reaction of normal locomotion, but it takes place so quickly 

 that it escapes observation as such in the rapidly moving organism. 

 Since it varies greatly in extent when it can be observed in operation, 

 it is quite possible that it is exaggerated in extent in moribund 

 individuals. It is not a pseudopodium either morphologically or 

 functionally. 



Its form is that of a blunt process with rounded tip and spreading 

 base. Its height varies but is greatest near the middle of the body 

 or just anterior to this level. It may attain a height equal to one-half 

 the transdiameter. In other cases the lobe is so broad at the base that 

 it gives a subtriangular outline to the body. 



The axostyle within the cytoplasm is so difficult to detect in life 

 that one cannot determine whether or not it shares in this movement. 



