118 
of 8 healthy females in which the coupling was completed by healthy 
males only three became pregnant, and in each of these cases the 
congress was repeated, occurring once in the evening of one day and 
again in the early morning of the succeeding day. In three of the 
unsuccessful cases the animals were separated after the completion 
of one congress, and in the remaining cases after the second congress, 
Seven ova were examined; four of them were from an animal 
killed 288 hours after, and three from animals killed 264 hours after 
completion of the second congress. 
The older ova were the smaller in size; they measured after 
hardening in PERENNYTs solution and spirit, 0,955 mm in diameter 
whilst the diameter of the younger ova, after the same treatment, 
was 1,232 mm. It must be noted, however, that the older ova were 
all obtained from an exceptionally small female. 
Five of the ova were hardened in PERENNYT’s fluid and spirit. One 
was hardened, in situ, in KLEINENBERG’s picro-sulphuric solution and 
one was hardened in FLEmMiING’s solution and alcohol. The first and 
second solutions both gave good results, out the ovum hardened in 
FLEMMING’s solution was comparatively useless when cut. 
Serial sections were obtained from six ova. Three series were 
double stained, two with hämatein and picric acid, one with picro- 
carmine. One ovum was stained with aniline blue black and two 
with logwood solution. The hämatein and picric acid gave the best 
results. 
All the ova were vesicular and of circular outline. When examined 
in normal saline solution they were opaque, their walls were granular 
and presented a spotted appearance which was due to the compara- 
tively dark nuclei scattered in them at irregular intervals. Cell out- 
lines were not distinguishable. 
At one pole of each ovum there was a darker granular mass, 
more or less regularly circular in outline but with a tendency in three 
cases to the assumption of a shieldshaped form. The margins of this 
mass gradually shaded off into the general wall of the cyst and it 
was impossible to decide, from surface view alone, whether the mass 
lay inside or outside the vesicle. 
After hardening and staining the ova presented a beautiful 
appearance. ‘he cellular wall of the vesicle could be distinctly seen 
inside the thin zona pellucida. Over the major part of the wall the 
component cells were readily observable, they were large and poly- 
gonal in outline and their nuclei were circular and of moderate size. 
The germinal area was now more distinctly defined; in the larger 
