32 University of California Publications in Zoology [Vol. 16 



can be detected ou opening the abdomen by the yellowish translucent 

 color and flaccid consistency of the wall at the point of infection. 

 In the case of infection by Trichomonas muris the intestine is less 

 inflated, the color somewhat duller, and the contents less gelatinous 

 and viscid. The two parasites occasionally occur together, but a heavy 

 infection by the one is not as a rule accompanied by a heavy infection 

 by the other. No cases of intestinal cancer coincident with infection 

 were noted, a single instance of axillary cancer being the only one 

 detected. 



The material has been prepared by smearing deeply from the fresh 

 intestinal wall, fixing in warm Schaudinn's fluid by the wet method 

 and staining in Heidenhain's iron haematoxylin. Cross-sections of 

 the infected intestine prepared with the same fixer and stain have 

 also been used. We attribute our success in finding the fission stages 

 to the use of smears well rubbed out to yield the deeply seated 

 parasites from the crypts, and from the epithelium itself, and also 

 to thorough search of the matm-ial. 



llORPIIOLOGY 



The actively swimming trophozoite (pi. 5, figs. 1, 4, and text fig. A) 

 is broadly pear-shaped in outline with semicircular anterior, and 

 convex-conical (70°-90°) posterior outline. Its total length, exclud- 

 ing flagella, is 1.25-1.50 of its greatest transverse diameter, which is 

 about 0.4 of the total length from the broadly rounded anterior end. 

 Posteriorly it tapers to an acute or even acuminate tip containing the 

 axostyle which does not protrude as in Trichomonas. In lateral view 

 (pi. 5, fig. 5; pi. 8, fig. 53) the ventral surface in the anterior 0.6 is 

 flattened, and more or less deeply cupped in a large ventral cup, or 

 so-called mouth, the cytostome {cyt., fig. A) which occupies nearly 

 the anterior half of the ventral surface and extends nearly from side 

 to side. Its outline and depth vary with the contraction of the 

 encircling peristome {ant. perist., post, perist., fig. A) and with the 

 distention of the body. In some eases (pi. 5, fig. 2) it extends posterior 

 to the peristome forming a recess, or may be very considerably reduced 

 (pi. 5, fig. 4), or fades out posteriorly as in some phases of mitosis 

 (pi. 6, figs. 16, 17), or disappears entirely as in multiple fission in 

 cysts. The dorsal outline in lateral view is much elevated, to a height 

 even exceeding a hemisphere or the transverse diameter, and is often 

 much higher than figui-ed (pi. 5. fig. 5, and pi. 8, figs. 53, 54), forming 



