No. 1.] ORIGIN OF HUMAN MONSTERS. 207 
graph. The structure of the walls of the two sacs is identical 
with that of the mesoderm of the chorion with all of the 
epithelial cells fallen off. ‘The two sacs do not communicate ; 
the larger has smooth walls; the smaller has numerous small 
vesicles, about 1 mm. in diameter, opening into it, and the 
cluster of “air cells” are directly blended with the mesoderm 
of the chorion. The specimen undoubtedly belongs to the 
vesicular forms, peculiar only on account of its size. 
No. 147. 
Ovum, 30 x 27 x 20 mm.; vesicle, I mm. in diameter. 
Dr. Pole, Baltimore. 
“Last period began January I, 1899, and the specimen was 
discharged March 23.” 
The ovum is only in part covered with villi, the remaining 
portion of the chorion being clear and transparent. The 
ccelom is completely filled with magma which has turned very 
white in the alcohol in which this specimen was preserved. 
Fic. 147.—Interior of ovum. Slightly enlarged. 
On one side of the ccelom, closely attached to the chorion, 
there is a small vesicle and an irregular mass which may 
represent the remnants of the embryo. 
Sections of the chorion show that the mesoderm is very 
fibrous and rich in cells. The vesicle within is about one milli- 
meter in diameter and is located two millimeters from the 
chorion, but not at all attached to it. Its walls are composed 
