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where. On the corresponding spot of the uterine wall a progressive 

 process sets in; first: formation of crypts by proliferation of epithelium, 

 at the same time thickening of the intermediate stroma; later by 

 this process a ring has been formed, which everywhere projects a 

 little into the lumen above the difïerentiation limit, dividing the cavity 

 of the foetal chamber into a mesometrally situated placentary part, 

 and an omphaloid part situated below it, while by this arrangement 

 the meanwhile completed diplotrophoblast (chorion) with its very 

 strongly thickened layer of trophoblast bulges out. The hyperplastic 

 stroma of the projecting ring is everywhere well provided with 

 crypts. 



In the meantime this proliferation process has been closely followed 

 by a regressive one; the epithelium begins to degenerate, first at 

 the surface, later deeper and deeper in the formed crypts; plasm 

 and nuclei become darker, more homogeneous, smaller; later the 

 pycnotic nuclei dissolve in the plasm and a mass is formed, epithelial 

 symplasm, in which finally greater and smaller vacuoles are e\enly 

 distributed. Everywhere short ramifications of epithelium have pene- 

 trated into the stroma, which soon degenerate. Also the stroma 

 itself undergoes similar alterations later. 



Wherever this degeneration has somewhat advanced, a third process 

 sets in, likewise extending as a band : the thickened trophoblast 

 penetrates with its ramifications some distance into the crypts, later 

 also between these into the degenerated mass. Here and there the foetal 

 mass thereby changes, after its elements have become enlarged and 

 paler, into a syncytium, the nuclei of which contrast well with those 

 of the maternal symplasm. In this connecting ring the syncytium 

 soon disappears again; extension causes the trophoblast with its 

 hollow ramifications, penetrating into the crypts, to become a single 

 layer once more; exactly here the area vasculosa still remains for a 

 time in connection with the trophoblast : everything pleads, in my 

 opinion, for the hypothesis that this has to be considered as a rudi- 

 ment, namely of an omphaloid placentation (Sorex, which among the 

 Insectivora stands nearest the Rodents, shows a distinct omphaloid 

 placentation). 



The products of the crypts and glands, transsudates and symplasm 

 masses, are shed over the cupola of the diplotrophoblast and probably 

 are resorbed by this latter. 



The vessels in the meantime proliferate strongly in the wall of 

 the mesometral part of the foetal chamber between the crypts, which 

 has remained unchanged yet; their wall consists as before of simple 

 endothelium, without a perivascular sheath. 



