low thick process (Placental Process Fig. 3) of the membranes is sent 
in. The cells of the outer layer of the serous envelope on this pro- 
cess are peculiarly modified, being columnar and their nuclei are 
larger, irregular in shape, and stain deeper. Many large vacuoles are 
found in these cells. There can be no doubt that these cells ab- 
sorb albuminous particles from the white. It seems to me that we 
have here in a very primitive condition the structure described by 
Duvar as the placenta in Birds. 
16. In hatching, the yolk-sac passes into the interior of the body 
where it lies for several months. 
2. Trionyx japonicus. 
17. In Trionyx, when the allantoic vesicle spreading into the 
extra-embryonic coelomic cavity, assumes a flattened shape, it is as 
represented in Fig. 4. It corresponds to Fig. 2 of Clemmys. The 
main point of dif- 
erence lies in the 
fact that in Trio- 
nyx, the left lobe 
is and remains to 
the end, rudimen- 
tary. The allantoic 
vesicle, instead of 
going round thesero- 
amniotic connection, 
producing the poste- 
rior constriction, as 
in Clemmys, 
pushes the connec- 
tion before it and 
makes it shift its 
position continually 
forward toward the 
anterior end of the 5 
egg. The result is ER pee 
that after a while, 
the seroamniotic 
connection becomes the most anterior part of the amnion, the main 
body of the amnion assuming the shape of a bag hanging pendant 
by the sero-amniotic connection. The final shape and arrangement 
of the foetal membranes are represented in Fig. 5 and Diag. VII. 
37 
Mer 
Right 
