362 A. A. W. HUBRECHT. 
the uterine swelling increase in size, and in Frommel’s figs. 
21, 15, and 138, the histological details closely correspond to 
what is in this memoir described and figured for the hedgehog 
(figs. 44, 47, and 57). It deserves special attention that also 
in the bat (according to Frommel’s figures) the deepest layer 
takes a much looser aspect, as if there the very elongated cells 
(which have a strong likeness to circular involuntary muscle- 
fibres) were rent asunder, leaving spaces between them that 
are exactly comparable to what is figured for the hedgehog in 
the very same layer on P]. XXIV, fig. 44, D’, and described on 
p. 884 of this article. Frommel calls this latter portion the 
“ Faserschicht ” (/.S. of his numerous figures); to the more 
compact outer portion with the very stretched cells (our 
fibrillar decidual layer) he leaves the general name of ‘“ Ute- 
russchleimhaut ” (U.S. of his figures). It is a curious fact 
that, whereas this separation of the deeper mucosa into a 
looser and a denser layer was noticed in the hedgehog in the 
majority of cases, it was much less conspicuous or even absent 
in a few (cf. Pl. XXIV, fig. 47). The same phenomenon 
appears to obtain in Vespertilio murinus, where the loose 
“ Faserschicht” can be hardly noticed in Frommel’s figs. 
22 and 21, it being eminently conspicuous in figs. 9, 11, 
and 15. 
Finally, I must challenge a comparison of Frommel’s fig. 22 
with Pl. XXVII, fig. 57 of the ripe hedgehog’s placenta, the 
typical points of agreement in the ripe stage being by such 
comparison none the less evident than in the earlier develop- 
mental phases. The fusion of the elements of trophoblast and 
allantois appears, however, to be still more complete in the 
hedgehog. Guided by what Frommel teaches us about the bat, 
and by what I have myself in this memoir advocated for the 
hedgehog, we may now return to Masius’ description of the 
rabbit, in order to call attention to the fact that it would 
appear from Masius’ description that a special layer, comparable 
to the trophospongia of the bat’s trophocalyx, and of the 
hedgehog’s trophosphere is not represented in the rabbit’s 
trophodisc. Perhaps the considerable part which the remains of 
