322 A. A. W. HUBRECHT. 
and figured in figs. 40 and 41. If we examine further sections 
of the series to which fig. 42 belongs it is there seen that they 
illustrate the process still more definitely. Such a section is 
here not figured, but if it is taken just outside of the blasto- 
cyst and its compact cellular investment 77. s we find that very 
numerous blood-cavities are there close together, and all of 
them with an extraordinarily proliferating endothelium. They 
are so close together that it can from them be well understood 
that a continuation of the same process must lead to absolute 
contiguity of the products, i.e. of the proliferated endothelium- 
cells. It is to this cell-mass of which we have just traced the 
maternal origin, that I propose to give the name of tropho- 
spongia. The blood-cavities inside of it have, as a rule, lost 
all trace of endothelium; in very rare cases in isolated spots 
traces of endothelium can still be noticed. Between the cells 
no remains of the decidual stroma as such can be detected, but 
this is immediately visible outside of the trophospongia. What 
is now and then—rarely though—found amongst these tropho- 
spongian cells are the remains of a gland and its epithelium, 
sometimes in the shape of an epithelial ring encircling a space 
that was formerly the gland cavity. We can well understand 
that such remains can occasionally be found embedded in the 
trophospongia if we turn back to fig. 89 and here suppose the 
process to have further advanced. Remains of the glands gl. 
would no doubt continue to be visible if the spaces c. a. and 
their endothelial lining increased so as to eliminate, in the 
immediate surrounding of the blastocyst, the interglandular 
connective-tissue stroma. It will at the same time be obvious 
that by the process here described a zone of modified cellular 
tissue is interposed between the as yet unaltered decidual 
stroma and the blastocyst. We have called the external epi- 
blast in which we have noticed proliferation the trophoblast, we 
have named the maternal, thicker layers the trophospongia. 
These two together, forming in Erinaceus a sphere which is 
shut off from the uterus lumen by the fusion of the lips of the 
decidua reflexa, should be indicated by the name of tropho- 
sphere, 
