1917] Boeck: Mitosis in Giardia microti 17 



on the two sides of the organism occurs. This is exemplified in figure 

 9, where the left nucleus is in the anaphase, and the right nucleus dis- 

 plays the four chromatic masses previous to their arrangement at 

 the equator of the spindle. Another case, earlier in mitosis, is seen in 

 figure 5. 



The chromosomes in the course of their migration fuse into two 

 chromatinic masses, one mass going to either pole (pi. 1, fig. 10; text- 

 fig. N). 



Telophase 



With the formation of each chromatinic mass produced by the 

 fusion of four chromosomes at each pole, the nuclear membrane begins 

 to constrict (pi. 1, fig. 10; text-fig. N). The completion of this process 

 results in two daughter nuclei (pi. 1, fig. 11; text-fig. 0) on each side 

 of the body. The upper two may still be connected by the small extra 

 nuclear rhizoplast to the blepharoplast nearest each centrosome ; the 

 intranuclear rhizoplast as yet has not been differentiated (pi. 1, fig. 

 11) but undoubtedly occurs later as an outgrowth from the linin sup- 

 porting the karyosomes. The reconstruction of the nuclei except for 

 this intranuclear rhizoplast is thus completed. The linin of the spindle 

 has again collected to form the network upon which the chromatin 

 of the karyosome is suspended. Mitosis is now completed and is to be 

 followed by plasmotomy. 



Plasmotomy 

 Plasmotomy, or the division of the parent cytoplasmic body to form 

 two daughter individuals, is not well understood. Only two cases 

 were found in my material, one of which is figured (pi. 1, fig. 15). 

 But from the study of these two stages and from like study upon 

 Giardia muris by Kofoid and Christiansen (1915&), the plane of 

 cleavage appears to be longitudinal, and the last point of cohesion 

 of the two daughter flagellates to be at their caudal areas. This 

 would result in the equipment of each daughter flagellate with two 

 of the daughter nuclei, an axostyle, and a complete peristome. 

 Whether or not this is the method in the case pictured in this paper 

 (pi. 1, fig. 15) cannot be definitely determined, for the anterior peris- 

 tomal fibrils of the lower daughter flagellate are fainter than those of 

 the upper but this may be due to the non-absorption of the stain. The 

 division of the cytoplasmic body is not equal in this case, but this 

 again is similar to cases found in Giardia muris (Kofoid and Chris- 

 tiansen, 19156). 



