36 CARL G. HARTMAN 
a side view of a spindle in which eight chromosomes are seen and 
short fibers are clearly outlined. The three sections shown in 
figures 15 to 17, plate 14, were cut tangentially through the egg, 
hence the polar body is cut longitudinally and the chromosomes 
are seen in polar view. 
The chromosomes in every case are short and thick, never 
characteristically rod-shaped. Some are hollow squares with 
rounded corners, others more perfectly ring-shaped. In side 
view several appear as short, thick rods, slightly constricted in 
the middle; others bent or cupped so as to appear narrowly 
kidney-shaped. The spindle is usually situated in a granular 
area free of vacuoles or fat globules; or, in other words, in the 
region of the spindle, the central and the marginal granular 
regions are bridged across. The polar body is usually placed 
near the chromosomes, as seen in the figures. In one case one 
chromosome was extruded with the polar body (fig. 8, pl. 14). 
c. The young uterine egg 
1. Size and shape. The appearance of young uterine eggs is 
well illustrated by the photographs in plates 1, 2, 5, 11, and 
others, which represent them with fidelity just as they were 
removed from the uterus. In size the eggs, as measured through 
the shell membrane, are subject to considerable variation among 
the different litters as well as to some extent within a given 
litter. Thus litter No. 342, consisting of about the 26-celled 
stage, average 0.7 mm., whereas the 4-celled eggs of litter 
No. 293 average 0.57 mm. and the eggs of litter No. 292, which 
are young vesicles of some 100 cells, measure 0.55 mm. Again, 
litters No. 336 and 337 average 0.73 and 0.50 mm., respectively, 
although they are in nearly the same stage of advancement and 
the ovum proper is of about the same size in the two litters. 
The differences in diameter among the eggs is therefore a differ- 
ence in the quantity of albumen deposited about the ovum. 
Figure 1, plate 12, represents an average unsegmented uterine 
ovum. 
