STUDIES IN MAMMALIAN EMBRYOLOGY. 369 
cases as to whether this neoformation should be called 
eminently perivascular or not. The proliferation is, more- 
over, distinctly different from the ulterior proliferation which 
gives rise to the maternal portion of trophosphere or tro- 
phocalyx, i.e. the layer of proliferated endothelium which I 
have called trophospongia. And when Frommel’s opposi- 
tion against Ercolani is thus formulated (1. c.), “the forma- 
tion of the decidual layer can easily be traced to a meta- 
morphosis of the subepithelial . . . cells of the interglandular 
tissue,” and if the author thereby means to imply that pro- 
liferation and neoformation do not come into play, I would 
point to the hedgehog as most decidedly in favour of the 
acceptation of a strong proliferative process such as Ercolani 
has first insisted upon. 
Frommel’s objections are all the more invalidated by the 
fact that the decidual layer of the bat, on which he bases those 
arguments against Ercolani concerning changes in the maternal 
interglandular tissue, is, as we have seen, synonymous with 
van Beneden’s plasmodiblast, which is by that author held to 
be, not of maternal, but of embryonic origin. Recent and 
older papers by Creighton, Robin, Tafani, Laulanié, Godet, 
and Mauthner are not noticed in this review, because they do 
not contain material that is in any way specially related to 
the questions that are brought forward in this paper, or that 
has not already been discussed in the preceding pages. 
Postscript.—The MS. of this chapter was ready for the press 
when No. 3, vol. ii, of ‘ Whitman’s Journal of Morphology ’ 
(April, 1889) came into my hands. In that number the im- 
portant article on ‘ Uterus and Embryo of Rabbit and Man,’ 
by C. S. Minot, is contained. This paper contains numerous 
points that invite a special discussion, both with a view to the 
actual results obtained in the hedgehog and to the results of 
other observers recorded above. The fcetal envelopes and the 
placenta were in the first place the object of Minot’s investiga- 
ciation of Ercolani’s work, of which the German investigators hold fit to 
think so lightly, 
