THE PLAOKNTATION OP PEEAMELES. 401 



this area. Abundance of lymph coagulum is found tiirough- 

 out the meshes of the delicate interglaiidular connective 

 tissue. 



The uterine glands liave not essentially altered since Stage B. 

 Some few of them, however, are now enormously enlarged, 

 and lined by a low cubical epithelium. 



In the allantoic placental area the gland openings are 

 occluded by the chorionic ectoderm cells, which at this stage 

 form an almost continuous layer firmly attached to the surface 

 of this portion of the syncytium. In the region surrounding 

 the allantoic placental area the gland openings are similarly 

 occluded by the close contact of the vascular omphalopleure 

 with the syncytial surface. 



The corium is now very richly supplied with blood ; the 

 capillaries are numerous and greatly dilated. 



Syncytium. — The syncytium in this stage is found to have 

 undergone differentiation into three fairly well-defined regions 

 corresponding to the three areas we have already distinguished 

 in connection with the foetal membranes, viz. the allanto- 

 chorion, the vascular omphalopleure, and the bilaminar ompha- 

 lopleure. The area of the syncytium to which the enlarged 

 ectoderm cells of the allantochorion are attached we shall 

 term the allantoic placental syncytium, as distinguished 

 from that portion of the syncytium in relation to the ompha- 

 lopleure. 



(a) Allantoic Placental Syncytium. — This is at once 

 to be distinguished from the remainder of the syncytium, not 

 only by the fact that the chorionic ectoderm is at this stage 

 firmly adherent to it, but also by the facts of its greater thick- 

 ness, and the larger size and deeper staining qualities of its 

 nuclei (figs. 6 and 7, ja/. syn.). It has now an average thick- 

 ness of 1 mm., i.e. it is just about three times as thick as the 

 syncytium in Stage B. 



The outer surface of the layer is not smooth, but wavy and 

 irregular, while its inner surface is distinctly lobulated. The 

 large and deeply staining ovalish or rounded nuclei are for the 

 most part closely aggregated together in nest-like groups in 



