204 



University of California Publications in Zoology [Vol. 20 



These structures traverse the cytoplasm, which is finely and uni- 

 formly granular and exhibits no evidence of cell inclusions or food 

 vacuoles and lacks alveolar differentiation. The peculiar anterior halo 

 around the blepharoplasts and the triangular halo between the postero- 

 lateral flagella seen by Kofoid and Christiansen (1915) in Giardia 

 muris are less sharply set off in Giardia enterica, in which the anterior 

 halo appears to be little more than the thinner anterior edge of the 

 body, and the triangular halo to show less contrast in density with the 

 adjacent cytoplasm than in G. muris. This "halo" or area takes on a 

 uniformly lighter tone as the plane of focus reaches it because of the 

 flattening of the ventral surface between the posterolateral flagella 

 which bound it. 



rig. D. Giardia enterica from vomit in case of carcinoma of the stomach. 

 After Zabel (1901, pi. 2, fig. 41). 



Fig. E. Giardia enterica attached to cells of the duodenum. After Miiller 

 ""8, pi. 2, fig. 2). 



There are no glycogen masses or granules in G. enterica, in either 

 the free or encysted stages. With Best's carmine (Prowazek and 

 Werner, 1914) the cytoplasm of the cyst stains a diffuse red, indicat- 

 ing diffuse paraglycogen. 



The cytostonie (cyt.) is the concave area on the anteroventral sur- 

 face encircled by the peristomal fiber. It is a sucker-like organ (pi. 23, 

 figs. 2, 3) adapted for adhesion to the tops of the epithelial cells (figs. 

 D, E) . Miiller (1890) found the flagellates on the cells of the jejunum 

 of an executed criminal at autopsy (fig. E) and Zabel (1901) found 

 them in place on the cells of epithelial fragments (fig. D) in the vomit 

 from a case of cancer of the stomach. The function of the cytostome 

 in attaching Giardia enterica to the cells of its host is thus proved by 

 observation to be similar to that of Giardia in rodents where exami- 

 nation of the relations of the parasite to the cells of the intestine of 

 the host is easily made. 



