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amniotic connection extended from the neck-region to the tip of the 
posterior amniotic tube, the proximal part of the latter remaining per- 
manent marks the posterior end of the sero-amniotic connection in 
all the later stages. 
9. How the proamnion of the head-region is replaced by the- 
ordinary amnion consisting of the epiblast and mesoblast is easily 
understood by a comparison of the Diag. IV and V. The mesoblastic 
Diagrams Mastrating 
Ihe De velopinent of he 
Foetn/ Membranes y 
Che/o ra 
ha. — Clenmys and 
Trronyx 
V/ —Clemmys. 
WAY Trign yx. 
wall of the extra-embryonic coelomic cavities of two sides is here 
united across (see 4), and insinuates itself between the epiblast and hypo- 
blast of the proamnion, peeling the latter off the former. Although 
the diagrams show the encroachment as taking place from before back- 
ward, it in reality takes place mostly from the sides. 
b) Origin of Allantois. 
10. The origin of the allantois is exactly the same as described 
for Birds by BaLrour in his Comparative Embryology Vol. II. 
c) Later Stages of Foetal Membranes. 
11. In later stages, Clemmys japonica and Trionyx japonicus 
present quite considerable differences, Clemmys being in my opinion 
more primitive in this respect than Trionyx. 
1. Clemmys japonica. 
12. The allantois is at first visible as a spherical vesicle in the 
extra-embryonic coelomic cavity, but soon being flattened, assumes the 
very peculiar shape sketched in Fig. 2. It is divided by two peculiar 
constrictions, anterior and posterior, into two parts of unequal sizes. 
The larger part is again subdivided into two lobes by the posterior 
set of blood-vessels. These two lobes of the larger part I have called 
the right, and the left, lobes, while the smaller half of the vesicle 
I have called the middle lobe. The two constrictions which divide 
