24 RICHARD ASSHETON AND THOMAS G. STEVENS. 
In fig. 15 certain long villous tufts may be seen. ‘These 
are villi which have passed through the homogeneous layer 
and presumably have penetrated into the uterine mucosa (or 
into glands). Some, we believe, have been torn off and left 
in the uterus (fig. 15, st. v.) (this, we believe, has also occurred 
in our full-term specimen), others have come out from their 
crypts (fig. 15, V”). 
It is extremely difficult to make out any epithelium cover- 
ing these villi. They are much branched and have small 
pieces of something identical or similar in appearance to the 
homogeneous material, which perhaps contains cells. Anyhow 
there is no definite epithelium. The mesoblastic core, which 
is thick and lobate, contains a more or less central vessel 
(artery ?) and a number of small capillaries arranged round the 
periphery—separated by a large amount of connective tissue. 
The pigment, which is so obvious a feature of the full-term 
placenta, is here hardly recognisable. A few fine granules 
may, however, be found over most parts. 
The branched villi (fig. 15, V V) close to the edge of the 
placental zone have a covering of trophoblast similar to that 
on the crowded villi of the zonary belt. ‘hey also are 
covered by the curious homogeneous layer which at the apices of 
the villiseems to be receiving nuclei from the foetal epithelium. 
The only difference between such a villous patch and the 
villi of the placental zone is that in the former the villi are 
less numerous and less crowded; in the latter they are much 
crowded. It is not difficult to conceive how an increase in 
size and number of villi such as those on the border (fig. 15, 
V V) might lead toaclose tangle of foetal villi originally diffuse 
and non-deciduate, especially if (as seems to be the case) 
they were prevented from penetrating the uterine tissues. 
Into this tangle a bleeding at the surface of the uterus 
might percolate, and so give rise to the system we have 
described above, by flowing at first between the villi (figs. 16, 
21, 24) and ultimately perhaps within the substance of a 
syncytium (fig. 18). 
We must leave for the present any further consideration of 
