410 MALL. [VoL. XII. 
the pedicle and between the vesicle and the chorion. With the 
exception of the allantois canal, Fig. 7 is a diagram of this 
specimen. No. XXXVII is much like No. XXI, but it did 
not stain well as the specimen was a number of years old 
when cut. 
Giacomini! has described a number of similar vesicles, and 
he expressly states that the vesicles had the structure of the 
umbilical vesicle, but that 
there was no trace of the 
amnion present in any of 
them. A number of other 
vesicular forms have been 
described, and in general 
they all appear much like 
the two specimens I have 
given. 
I do not think that it 
is rash to assert that 
these vesicles represent 
an arrested development 
of an earlier stage, which, 
due to impaired nutrition, 
or whatever it might have 
been, simply allowed the 
Pi, 6 Dlannade Senie ot Ballots Host embryonic vesicleto keep 
drawn only on the upper side. ec, ectoderm; ex, On expanding. That this 
entoderm ; wes, mesoderm ; 2 v, umbilical vesicle ; 
coe, coelom; al, allantois ; a, amnion. 

expansion can keep on is 
already shown in the sim- 
ple enlargement of the chorion after the embryo is distorted 
or wanting altogether. We have in these specimens a thin 
chorion with atrophic villi, and why can we not have an 
expanded and atrophic embryonic vesicle if its development is 
impaired? In this way I view specimen No. LVIII. It 
represents a much earlier stage, which has simply expanded and 
was ultimately aborted. In No. LVIII the embryonic vesicle 
must have ceased its further development a week or so before 
the abortion, about the time the coelom was beginning to 
1 Giacomini: Ergebnisse d. Anat. u. Entwicklungsgesch., Bd. 4, S. 636. 
