1917] Boeck: Mitosis in Giardia microti 5 



and presents an appearance not unlike that characteristic of Giardia 

 intestinalis (see Rodenwaldt, 1911). 



The cytoplasm is finely granulated, sometimes appearing quite 

 uniform in texture, except at the time of and during encystment, 

 when some degree of coarseness is usually present. The cytoplasm in 

 the area of the cytostome and in the triangular halo enclosing the 

 caudal portion of the axostyle and bordered by the intracytoplasmic 

 portions of the posterolateral flagella is of a still finer constituency and 

 more finely granulated than that in the other parts of the body. 



Compared with G. muris, the species found in culture mice and 

 Peromi/scus gamheli (See Kofoid and Christiansen, 1915&), G. microti 

 is found to be from two to three fx longer, but somewhat narrower. Its 

 caudal area is more tapering, resembling that of G. intestinalis as seen 

 in the microphotographs by Rodenwaldt (1911). There is some indi- 

 cation that the cytoplasm of G. microti is more finely granulated than 

 that of G. muris. The parabasal bodies in G. microti are usually 

 slender, elongated bodies, lying dorsal to and across the axostyle, while 

 in G. muns these organs are ellipsoidal bodies lying dorsolaterally on 

 either side of the axostyle. The cytostome in G. microti is seen to 

 extend more nearly to the periphery of the body than that in G. muris. 



The body contains the following morphological structures: the 

 axostyle, lying medially upon the ventral surfce of the body ; two 

 nuclei, in the cytostomal area and near the axostyle; a centrosome, 

 embedded in the nuclear membrane at the anterior pole of each 

 nucleus; the rhizoplasts, connecting the two nuclei with centrosomes 

 and the blepharoplasts and within the nucleus with the central karyo- 

 some ; and two blepharoplasts (united by an anterior commissure), 

 situated on the anterior end of the axostyle. A temporary paradesmose 

 stretches between the divided centrosomes of each nucleus at the time 

 of mitosis. The anterior chiasma is the point of intersection of the two 

 anterolateral flagella arising from the blepharoplasts. These flagella 

 after leaving this point pass to the side opposite that from which they 

 originated. The anterior and posterior peristomal fibrils border the 

 periphery of the cytostome ; the anterior right and left fibrils are 

 thicker than the posterior fibrils. The parabasal bodies, composed of 

 one or two bands of chromatic material, are situated in the posterior 

 third of the body, and lie upon the dorsal surface of the axostyle. 



There are eight flagella: a pair of anterolaterals which border the 

 anterolateral edges of the animal ; a pair of posterolaterals whose 

 intracytoplasmic portions bound the outer limits of the clearer cyto- 



