22 RICHARD ASSHETON AND THOMAS G. STEVENS. 
We incline to the latter hypothesis. Firstly, because there 
are no cells or nuclei in the plasmodium which seem to be the 
parent cells of these corpuscles. Secondly, at the heads of these 
new channels the contained corpuscles are not, as far as we 
can judge, undergoing multiplication, while we can find 
places, in the larger channels, where they are certainly being 
formed. ‘Thirdly, we can find no intermediate stages between 
the unbroken plasmodium and the clear space containing 
separate corpuscles. 
As favouring the other view there is the fact that there are 
no non-nucleated red corpuscles at all in these newest 
channels. We find them only in the larger or older channels. 
Although we cannot speak positively about the origin of 
these corpuscles, we have some evidence of their immediate 
formation. 
In the larger channels there are large numbers of red 
non-nucleated blood corpuscles, and large numbers also of 
nucleated corpuscles, some with more than one nucleus and 
quantities of bodies of all sizes which stain deeply which 
seem to be fragments of nuclei (fig. 22). 
Also near the margin are numbers of large cells, sometimes 
elongated and almost endothelial in position, which in some 
cases appear to be breaking up, and in others to have more 
than one nucleus. We regard these as the parent cells of 
the nucleated corpuscles within the channels, but the question, 
which must remain unanswered for the present, is what is the 
actual origin of these mother cells? We do not find them in 
the small channels, but we can trace them back into the 
largest channels and even into the large vessels (fig. 29), 
which occasionally occur and are evidently the connecting 
vessels between the placental blood system and the vessels of 
the uterus, which we are inclined to consider maternal 
(fig. id, and fig. 1 b. U. V. A.). An hypothesis not without’ 
some evidence to support it would be to suppose these cells 
to be of maternal endothelial origin, and to become gradually 
washed along the newly formed channels, adhering for a 
while (after the manner of white blood corpuscles) to the 
