360 G. CARL HUBER 
the abnormal stages met with seems warranted, especially in 
view of the fact that the literature is very meager in its ac- 
count of early stages of mammalian ova presenting abnormal 
development. 
The excellent and comprehensive studies of Mall on pathologie 
human ova, extending over many years, may be interprete as 
leading to the general conclusion that pathologic ova and mon- 
sters ‘‘are produced from normal eggs by conditions which either 
interfere with their nutrition or poison them.” There is evi- 
dence to show that defective implantation, using the term in its 
broadest sense so as to include relation to the embryotroph or 
pabulum, is directly associated with abnormal development. 
Comparative experimental teratology so successfully followed by 
a number of Kuropean and American experimental embryolo- 
gists warrants the conclusion that all of the abnormalities or 
malformations observed in the human embryo may be brought 
forth by the application of suitable mechanical interference or 
chemical solutions. Experimental teratology possesses the very 
great advantage of enabling the observer to follow the pathologic 
process from step to step, admitting more readily of their inter- 
pretation, than when single stages are obtained from nature. 
The evidence appears to be accumulating that the primary causes 
which produce pathologic ova lie not in the germ cells, but are 
rather to be sought in the environs of the germ cells in the course 
of their development. 
I am cognizant of the fact that the interpretation of the chance 
findings of abnormal stages of mammalian ova is much more 
diffeult than of abnormal ova produced experimentally. The 
fact, however, that nearly all of the abnormal ova observed by 
me in my albino rat material were found in tubes and uteri con- 
taining normal ova also, tubes and uteri which so far as observ- 
able appear in most instances to be normal, and the further fact 
{hat certain of the abnormal ova are of stages prior to what may 
be regarded as showing implantation, stages concerning which 
we possess no data as far as human ova are concerned, has lead 
to the tentative conclusion that certain of the abnormal ova 
may be the resultant of abnormal germ cells, perhaps of an 
abnormality which may not show a structural expression. 
