GERM CELLS IN ASCARIS INCURVA 83 



It is not intended here to discuss the various theories of mitosis 

 but merely to note the possible application of one or two. 



The conditions may be interpreted by the theory of electrical 

 repulsion (Lillie '05) — the metaphase plate being formed by 

 repulsion of the negatively charged chromosomes from the 

 negati\'e astral centers. Here the seven smaller X-chromosomes 

 being univalent remain in the plane of the metaphase plate, 

 while all others due to repulsion of like charges (Gallardo '09) 

 separate and form an extended ring (figs. 18, aandc). This 

 latter formation is such as would be expected from a group of 

 mutually repellent bodies united by fibers, and thus in this 

 case, if it be assumed that these forces operate only during the 

 first phase of mitosis, there does not exist the objection to the 

 theory pointed out by Conklin ('12) in that anaphase chromo- 

 somes do not separate as if carrying like charges but tend rather 

 to mass together. 



During the second phase the evidence indicates that these 

 forces no longer operate and the movements seem more readily 

 explainable by the \'ortical cytoplasmic movements or diffusion 

 currents (Butschli '00, Conklin '02) producing a flow outward 

 from the center of the spindle to either pole and thus carrying 

 out the anaphase plates. It may also be noted that the ap- 

 pearance of the cleavage furrow is coincident with this change 

 and this also has been associated with vortical cytoplasmic 

 mo^'ements which shift the cytoplasm from the equatorial plane 

 to pass in part through the spindle to either pole (Conklin '02). 



SIZE dbiorphis:m of spermatozoa 



Measurements have been made of 600 nuclei of spermatozoa 

 and a marked dimorphism of size is shown. The cells examined 

 were from preparations from the uterus as frequently mature 

 spermatozoa are not found in the testis (Tretjakoff '05, Romieu 

 '11). The nucleus is a thick circular disc. Its position in the 

 cell is variable, a frequent condition is shown in figure 49, a 

 side view and figure 48, an axial view of a spermatozoon. All 

 measurements have been made from one slide (sectioned material) 

 stained in saffranin and light green. The compact nuclei stain 



