Bey CARL G. HARTMAN 
that such eggs may easily be taken for cleavage stages (fig. 5, 
pl. 11). I have never seen a mitotic figure in such degenerating 
eggs. The eggs shown in the photograph in figure 8, plate 1, 
remained in the uterus until near the end of the sixth day after 
ovulation. 
4. The pronuclear stage. Several eggs were studied at this 
stage, although I did not secure an entire litter of eggs con- 
taining pronuclei. The pronuclei at first lie at the periphery 
of the ovum in a homogeneous granular area devoid of fat 
globules. Eventually they come to lie near the center of the 
egg where the first cleavage spindle will form. The chromatin 
of the pronucleus is in most cases very diffuse and stains weakly. 
Two figures of the stage are given in the writer’s former paper 
and figure 20, plate 14, is an ovum with two nuclei which differ 
from the nuclei of the other members of this litter (2-, 3-, and 
4-celled eggs); hence I regard this egg as in the pronuclear 
stage. 
d. The first cleavage 
1. The first cleavage spindle. No new material containing the 
frst cleavage spindle has been obtained recently. In figure 21, 
plate 14, I have redrawn specimen 52 (3) as a composite of four 
sections, which were taken obliquely through the spindle, which 
lies in the central yolk-free zone of the egg. The fat vacuoles 
are evenly distributed at the poles and some of the yolk has 
already been extruded, chiefly on one side of the egg. 
2. The 2-celled stage. The early cleavage material in the 
writer’s collection was, however, considerably increased by 
recent accessions, namely, from the following litters: No. 173, 
which furnished 3- and 4-celled eggs; No. 203, which furnished 
four 2-celled, one 3-celled, and the rest 4-celled eggs; and No. 306, 
which furnished, besides a number of eggs that were unfor- 
tunately lost or misplaced, two 2-celled and one 3-celled egg. 
All of these litters are the product of the left uterus and in each 
case a later stage was removed from the right uterus, which is 
good evidence that we are here dealing with normal fertilized 
material. 
