No. 3.] UTERUS AND EMBRYO. 423 
previously described, §§ 14, 15; the chorion is bounded against 
the decidua by an epithelium c, which I interpret as the chori- 
onic ectoderm; there is no trace of a second layer of epithe- 
lium; so that the uterine epithelium must be considered lost, a 
conclusion agreeing with the observations of Kolliker, Turner, 
and myself upon earlier stages, and the statements of Ercolani. 
The decidua has eight or nine times the thickness of the cho- 
rion ; it has an upper compact and a lower cavernous layer; the 
former contains numerous decidual cells, most of which are a 
little larger than those nearer the muscularis; the compact 
layer contains a few blood-vessels of moderate calibre, and occa- 
Cut 34.— Uterus about seven months pregnant; upper portion of decidua vera, 
with the chorion leve zz sztu. mes, mesodermic layer of chorion; ef, epithelial 
layer of chorion; D', decidua. X 340 diams. 
sionally a large vessel, v, surrounded by connective tissue contain- 
ing no decidual cells. Examined witha higher power, the decid- 
ual cells —compare Cut 34, D!—are found to resemble quite 
closely those at one month, Cut 30, but they are much more 
numerous and closer together, and their processes are fewer ; 
they vary also more in size; some of the larger ones are multi- 
nucleate; it is probable that the cells are multiplying by divis- 
ion; the matrix presents a fibrous look, but whether it contains 
actual fibres, I am not sure; between the decidual cells are a 
