STUDIES IN MAMMALIAN EMBRYOLOGY. 345 
through the wall of one of the larger decidual Jacune; the 
contents of the latter are then seen to make their way out of 
the lacunz amongst the deciduofracts, and from thence further 
into the trophoblastic lacune. This was already indicated 
by the presence and distribution of maternal blood-corpuscles 
in this region, but raised to absolute certainty by the effects 
of the injection from the maternal arterial system. Parallel 
with this liquefaction and resorption of decidual tissue other 
deciduofracts are seen to make their way centrifugally by 
meaus of the decidual lacune that have once opened out into 
the trophoblast, and it is by that means that a further resorp- 
tion of decidual tissue, simultaneously with the increase in 
size of the enclosed embryo, is prepared and accelerated. 
Finally, it was found that in certain preparations remnants 
of glandular elements had longer resisted the action of the 
supposed phagocytal elements (pp. 322, 327), and by their 
presence amidst the tissues of the trophosphere appeared to 
betray a more active participation of the latter in the gradual 
reduction of the decidual proliferation. The fact that during the 
development of the embryo this decidual tissue arises ad hoc, 
obliges us to inquire carefully into the part it has to play in 
the economy of the embryo. We have learnt to appreciate its 
significance in the origin of the reflexa, in the preparation of 
blood-cavities, and in the formation of the trophospongia. It 
may well be asked if it might not be considered probable that— 
before portions of it become membranaceous—part of its proto- 
plasmatic matter has undergone resorption and served nutri- 
tory purposes? Once the decidua reflexa and the omphaloidean 
trophosphere having been converted into a membrane, the 
sphere of activity, and with it the physiological significance of 
the deciduofracts, would evidently be reduced. Even if the 
questions here referred to may all be answered in the affirma- . 
tive, it will further have to be made out in what way the 
material directly absorbed by the deciduofracts is again 
utilised in the further economy. Masquelin and Swaen have 
insisted upon the significance of cells of the decidua for the 
formation of blood-corpuscles. Frommel has partly followed 
