No. 3-] UTERUS AND EMBRYO. 361 
by multinucleate cells (compare Fig. 14, Pl. XXVIIL, of these 
cells from an older placenta) ; their origin appears to be due to 
the development of clusters of connective tissue cells, which lie 
scattered about between the blood-vessels ; each cluster consists 
of from three to six cells lying together and connected on the 
one hand by short processes with one another, and on the other 
by longer processes with the cells of adjacent clusters. The 
larger clusters are separated by membranes from one another, 
and thus every cluster becomes enclosed in a membrane and ap- 
pears as a multinucleate cell. The development of these cells 
would doubtless repay more accurate investigation. The multi- 
nucleate cells do not yet form a continuous bed under the 
placenta, but are divided into parts by masses of very loose 
connective tissue. At the base of the fissure between the two 
lobes of the placenta the glands have almost entirely disap- 
peared, but we still find a few unresorbed fragments of their 
degenerated epithelium; these fragments are conspicuous by 
their very deep staining, both of the hyaline substance and of 
the nuclei: the neighboring tissues are less colored. The fissure 
itself is like an inverted L; that is, it is transversely expanded 
at the base; the floor of the expansion is thrown up into folds 
and covered by a cylinder epithelium, which I feel some hesita- 
tion in designating as the regenerated uterine epithelium, al- 
though it resembles the epithelium on the peri-placenta, where 
the glands are resorbed and the epithelium reconstituted from 
its degenerated self. On the other hand, as shown in the next 
section, there is some proof that the foetal ectoderm penetrates, 
by villous growths, far into the placenta. It seems possible that 
the fissure is filled by villous excrescence of foetal origin and 
that the epithelium of the sub-placenta belongs to the villus. 
This view does not commend itself to me. Neither upon the 
upper wall of the expansion nor on the sides of the fissure have 
I recognized any epithelium. The upper part of the fissure is 
closed by an ingrowth of connective tissue. Hence the lower 
part is changed into a shut cavity in the centre of the placenta, 
and into this cavity the folds covered with epithelium project. 
So far as I am informed, this curious structure has not been 
described hitherto, but what appears to be clearly its homologue 
has been observed by Ercolani, 89, pp. 290, 291, Tav. IV., Fig. 
I., O, and specially studied by Creighton, 77b. Both of these 
