156 MALL. [Vov. XIX. 
The smaller vesicle is lined with a layer of large spindle- 
shaped cells. Migrating cells are within the cavities of both 
vesicles, and are also scattered throughout the surrounding 
magma. 
There are no blood-vessels in the chorion. The syncytial 
layer is diminished, but is well formed upon the tips of the 
villi. Here it often accumulates in layers, forming peculiar 
strata. 
Fic. 21c.—Section through the vesicle and chorion. X 25 times. The 
second vesicle between the larger one and the chorion appears to 
be the stem with a dilated allantois, although it is not attached to 
the chorion. 
No. 24. 
Chorion, 21 x 16x 5 mm. 
From Dr€, OO) Milles Baltimore. 
The ovum was covered completely with villi which branch 
a number of times. Upon opening the specimen it was found 
that the coelom was filled completely with magma reticulé 
of moderate density. No trace of an embryo could be found. 
From time to time I made renewed search and finally decided 
to cut the entire specimen into sections. After staining it 
with cochineal a small nodule became visible when the speci- 
men was placed in direct sunlight. This, with a piece of 
chorion upon which it lay, was cut into serial sections 20 
microns thick. 
The walls of the vesicle are composed of three layers, the 
outer being greatly thickened at points, but retains sharp 
