1617 
not of great importance. The main fact is that the embryonic knob 
is pushed into the protective trophoblastbladder, either by invagina- 
tion or by solid proliferation. Moreover in how many cases do not 
these two processes take each other’s place, without it being possible 
to settle which mode of development is the more primitive one? 
After being definitely separated from the diplotrophoblast the 
amnion cavity may increase along with the growing embryo, without 
being impeded by its connection with the surface of the fruitbladder. 
Gradually the room of the latter will be filled up for the greater 
part by the amnioncavity and in this way the latter takes upon itself 
the protective function exercised in the beginning by the trophocoel 
or by the exocoeloma. 
In this paper [ will not digress on the changes in the method 
of development of the primary egg membranes within the class of 
Mammals, since I should be obliged to repeat many things, which 
have been set forth in so excellent a manner by Hvsrecut and his 
pupils. I cannot avoid however making a few remarks upon the 
other foetal appendages: 
1. Allantois. We have seen that in early stages of (phylogenetic 
and ontogenetic) development the connection between the embryonic 
area and the respiratory and nutritive diplotrophoblast is secured 
by the caudal connective stalk. This stalk arises at the ventral side 
of the blastoporus and turns dorsal to the surface of the germbladder. 
As the amnion-cavity grows ventral, it is turned also to the ventral 
side and may be called with His ventral stalk (Bauchstiel). 
If the connection between maternal and foetal circulation is very 
intimate, the osmotic interchange between these systems is intense 
enough to remove obnoxious excretory products out of the foetal 
circulation, a condition realised e.g. in Primates. If the connection 
between mother and fruit loosens or if implantation takes place at a 
later period, the excretory products must be stored up in a way 
that will not cause inconvenience to the embryo. For this purpose 
the embryonic urine-bladder, the allantois increases. As this organ 
is situated near the point of attachment of the connective stalk 
to the embryo, it is plausible that it will grow along the stalk 
in order to remove as soon as possible from the embryo and gain 
the surface of the fruitbladder where the opportunity for osmotic 
interchange is greatest. In this way the allantois will come in contact 
with the bloodvessels of the connective stalk and the diplotrophoblast 
(allantoidean vessels, see above) and will assume a respiratory and 
nutritive function. The fact that in most cases the so-called meso- 
dermal allantois (in my opinion a relic of the connective stalk) 
