STUDIES IN MAMMALIAN EMBRYOLOGY. 8347 
the description of the full details of this phenomenon for 
another publication, and here content myself with pointing out 
the great difference between mole and hedgehog in this respect. 
The fact itself had to be stated because I shall have to return 
to it in the course of the theoretical speculations of the next 
chapter. 
As was already noticed above (p. 310), the hedgehog’s 
after-birth shows the foetal membranes attached to its border: 
they have been ruptured in order to give passage to the embryo. 
The yolk-sac is attached to that portion of the membranes 
which is directly opposite to the placenta itself. A distinct 
point of severance between yolk-sac and embryo can with diffi- 
culty be indicated in the after-birth: one between embryo and 
allantois is all the more distinct. As was described before 
(p. 808), the allantoic vessels are not united into an umbilical 
cord with the stalk of the yolk-sac, but they go round the side 
of the foetus, and are attached to the placenta behind its back. 
We find these vessels in the cast-off after-birth, united into a 
lengthened string which simulates an umbilical cord. This 
vascular string undoubtedly breaks off from the new-born 
hedgehog’s navel at the time of birth, by far the longer portion 
remaining attached to the after-birth. The young hedgehog 
itself only shows a very short remnant of the tissues by which 
it was united to the uterine wall, and this soon decays and 
disappears. 
The way in which, after parturition, the epithelium of the 
mucosa has become restored and ready to recommence the 
cycle of pregnancy has been sufficiently described in the pre- 
ceding chapter (p. 336), and need not be again noticed here. 
IV. Recent Authors on the Phenomena of 
Placentation. 
I have purposely refrained, in the preceding section of the 
ext, from giving any comparative account of the data furnished 
by other authors with reference to other genera of mammals, 
This was done not to obscure the description of phenomena, 
which in themselves are complicated, and can only be well 
