1923] Kofoid-Swezij: Prntatricliomonas ardin delteiJi 381 



tapers posteriorly asymmetrically. A dark tibrillar line forms its 

 margin. We are unable to find a tibrillar connection between this 

 margin and a blepharoplast such as we found (1920) in Chilomastix. 

 It abuts directly upon the secondary blepharoplast and may have a 

 connection with it. 



The nucleus {nuc, fig. A) varies greatly in size, ranging from 

 two to four microns in diameter. It is smaller directly after mitosis 

 in some instances (pi. 37, fig. 5). It is usually spheroidal, but 

 occasionally ellipsoidal with the longer axis anteroposterior. It is 

 located anteriorly, never more than 0.5 its diameter from the blepharo- 

 plasts and usually almost in contact with them. Its membrane is 

 lightly encrusted with peripheral chromatin and at its center there 

 is often a single, spherical karyosome of variable size (pi. 37, figs. 

 3, 4). In some instances there are two such chromatin masses (pi. 37, 

 figs. 2, 7 ) which suggest the early prophase of mitosis. In one instance 

 (pi. 37, fig. 10) of a late telophase, an intranuclear rhizoplast runs 

 from the centrosome to the chromatin mass. 



The cytoplasm of this species is generally rather coarsely vacuo- 

 lated, except during binary fission. The vacuoles may contain red 

 blood corpuscles in various stages of digestion, or clusters of bacteria 

 or food remnants (pi. 37, fig. 3). We have not observed in this species 

 the sloughing off of cytoplasmic blobs which we have previously noted 

 in Trichomonas (1915) and Chilomastix (1920). 



The shape of the body on stained slides is stout pyriform, tapering 

 posteriorly with a slight asymmetrical taper anteriorly also to the 

 region of the blepliaroplasts. It is more rotund on the side of the 

 cj'tostome. Posteriorly it tapers in an asymmetrical cone of forty-five 

 or more degrees. The taper at the two ends is .such as almost to give 

 an asymmetrical biconical shape to the body, the convexity is some- 

 what greater on the side of the undulating membrane. In life the 

 length is often twice the greatest diameter, or even more, and the 

 asymmetry of the apex more marked than in stained individuals. 



The dimensions of Pentatrichomonas in fresh stools and in cultures 

 vary considerably. The length of twenty-five individuals measured 

 from the anterior tip of the body to the posterior end of the cytoplasm, 

 but not to the tip of the axostyle, ranged from 9 to 20 microns, aver- 

 aged 14.6 and had its mode at 14 microns. The width ranged from 

 7 to 14 microns, average 9.3 and had its mode at 10 microns. A 

 rounded-up individual measured 9 by 9 microns. These measure- 

 ments were made on material stained in iron haematoxylin. In life 



