PLACENTATION OF THE SEALS. 281 
along with the placenta consists of the delicate easily torn processes which dip 
into the secondary and tertiary fissures, and are entangled between the placental 
lobules and amidst the foetal villi. The uterine face of the separated placenta 
is not covered by a continuous layer of decidua, for the greater part of the 
mucosa is not shed when the placenta is expelled, but remains as a layer of 
membrane of considerable thickness on the inner surface of the muscular coat, 
and presents on its placental aspect numerous irregular pits or trenches into 
which the convolutions of the placenta are received when the organ is in sétu. 
Before describing the minute structure of the serotina, I shall relate some 
observations on the structure of the mucosa in the non-gravid uteri of some 
seals, which I have had the opportunity of examining, and also the structure 
of the uterine mucosa in the gravid uterus of H. gryphus, both in the non- 
gravid horn and in the non-placental area of the gravid horn. 
In the non-impregnated uterus of a young seal (species unknown) elon- 
gated, tubular, utricular glands were very numerous, and closely packed together 
in the mucosa. The glands lay perpendicular to the plane of the surface, were 
tortuous, and apparently branched at their deeper ends; by their opposite 
extremities they opened by funnel-shaped mouths on the free surface of the 
mucosa. They were lined by a columnar epithelium, and possessed a central 
lumen. The interglandular connective tissue contained multitudes of corpuscles. 
I obtained in 1870 the non-gravid uterus of an adult grey seal (HZ. gryphus) 
from a specimen captured in that year off the coast of Fife.* The uterus was 
empty, and the cavities of its horns contracted, but as the uterine veins were 
dilated, and a large vascular corpus luteum was present in the left ovary, I con- 
cluded that the animal had been delivered of a foetus not long before her 
capture. When the uterus was opened the mucous membrane was seen to 
form strong folds extending in the longitudinal direction. By its deep surface 
this membrane was connected to the muscular coat by a lax connective tissue. 
Vertical sections through the mucosa, examined microscopically, displayed 
numerous tubular glands, which opened freely on the surface. Their main 
stems lay almost perpendicular to the plane of the surface, but as the glands 
were somewhat tortuous, and gave off lateral offshoots, they were not un- 
frequently transversely or obliquely divided. The epithelium did not fill up the 
gland tubes, but left a central lumen. The exact form of the epithelium cells 
could not definitely be made out, but the end which lay next the lumen was 
rounded or somewhat polygonal, like the broad free end of a columnar epithe- 
lium cell. The interglandular connective tissue was vascular, and a well-marked 
capillary plexus ramified immediately beneath the surface of the mucosa around 
the mouths of the glands. 
* The capture of this specimen is recorded in the “Journal of Anatomy and Physiology,” vol. 
iv. 1870. 
