92 MALL. [Vor. XIX. 
I shall first consider those ova in which the embryo, or 
embryo and cord, has been destroyed, leaving only the 
amnion, and will leave the ova or moles with pathological 
embryos to follow. There are many of them, and when they 
are classified in weeks they tell a continuous story. 
Table IV gives the list of ova in which the amnion is 
retained, with such other data as I have been able to collect. 
Unfortunately, the data relating to the age of the specimens 
are very incomplete. However, it is possible to connect the 
specimens in a satisfactory way if we begin with those which 
have remnants of the embryo attached to the cord, and 
gradually proceed to those in which the cord is destroyed 
entirely, leaving only the amnion and the chorion. 
In general, the size of the chorion and cord do not corre- 
spond properly with each other, showing that either one or 
the other has been retarded in its growth. In specimens Nos. 
130 and 32, for instance, the embryo masses are of about the 
same size, representing cords of the second month, but one is 
from a small and young ovum and the other is from a large 
and much older one. It is fair to assume that the embryo in 
No. 32 was destroyed when the ovum was as small as No. 
130 is at present. 
Table IV gives a list of the specimens with all stages of 
destruction of the embryo after the amnion is well formed, 
leaving only a portion of the embryo, or, in extreme cases, 
the umbilical cord alone. In a few of the specitmens the cord 
is also destroyed and in them the chorion is lined simply by 
the amnion. The villi of the smaller ova of this group appear 
quite normal, and for this reason I have been inclined to 
think that in them the primary cause lay in the embryo 
itself, and that in the older stages the changes found in the 
chorion were of a secondary nature. Further investigation, 
however, may reveal the same early changes in the neigh- 
borhood of the villi here as are found in the specimens 
in which the embryo and amnion were destroyed during 
the first four weeks of pregnancy (Table III). Here also the 
earlier specimens, those with numbers lower than 150, did 
