No. 1.] . ORIGIN OF HUMAN MONSTERS. 81 
syncytium. The growth of the syncytium appears to have 
been violent, and it encroaches upon the mesoderm of the 
chorion, which at points is beginning to be fibrous. Here also 
the primary trouble seems to be due to the mucus and pus 
which bathe the villi of the chorion; they naturally cause 
havoc with the nutrition of the ovum. 
The next specimen of this series (No. 264) is a very valu- 
able one, for its tissues, from the embryo to the decidua, are 
unusually well preserved and the menstrual age is given. The 
chorion is fibrous and thickened, and between the villi there 
is mucus which is well infiltrated with leucocytes. The coelom 
is very small, but 10 mm. in diameter, and is filled with a 
mass of hard hyaline magma. 
The embryo is represented by a vesicle composed of two 
layers, the outer of which is much thickened at its attach- 
ment to the chorion. Here it is decidedly mesodermal in 
character and contains many large blood-vessels, filled with 
blood, which spread into the chorion. In the tissues around 
these. blood-vessels there are many round cells which are 
similar to, and no doubt have come from, the embryo’s blood. 
Many round cells are also scattered through the magma. 
A similar remnant of an embryo may be seen in specimen 
No. 14. The mesoderm is very fibrous and extends over the 
vesicle within. Within the chorion there are groups of epithe- 
lial cells which are no doubt derived from the syncytium. 
There are a few blood islands at the base of the nodule and 
two other spaces lined with spindle-shaped cells. The main 
cavity of the nodule is lined with epithelial cells, which no 
doubt represents the yolk-sac cavity. 
No. 147 is a specimen much like No. 14, giving, however, 
its menstrual history, which makes it eighty-nine days old. 
The chorion is fibrous and partly covered with villi and the 
coelom is filled completely with magma reticulé. Lying in the 
magma, but detached from the chorion, there is a small vesicle 
one millimeter in diameter. One-half of the vesicle is com- 
‘posed of the single inner layer, and on the other there is an 
additional thick outer mesodermal layer, in which there are 
