EXPERIMENTALLY PRODUCED EXTRAUTERINE PREGNANCY. 7 1 



must in fact occur more frequently than the direct findings 

 suggest. We have to deal with formations which resemble closely 

 structures of the embryonal placenta, and they originate in 

 ovarian follicles. They are either well preserved or are found in 

 the process of retrogression and in the end are substituted by 

 connective tissue. In two cases I was able to find besides em- 

 bryonal structures proper, for instance the Anlage of the nervous 

 system. It had been known previously and I myself had de- 

 scribed processes which had to be interpreted as the first seg- 

 mentations of eggs in atretic follicles which in consequence of 

 the abnormal conditions under which they took place followed as 

 might have been expected an abnormal course. ^ The interpre- 

 tation that we have to deal merely with the disintegration of the 

 ova can be excluded with certainty. Such an interpretation 

 would be contradicted by the regularity of the divisions. Fur- 

 thermore we may find in these various segments either nuclei or 

 the remnants of nuclear spindles and I was able to observe the 

 simultaneous presence of a mitosis in each one of the two such 

 segments. These segmentations also are found chiefly in the 

 ovaries of the young guinea pigs. A somewhat furthergoing 

 formation of the first segments in ovarian eggs has recently been 

 described in armadillo by Newman.^ ' 



In all these cases we have merely to deal with the first parthe- 

 nogenetic segmentations of the ovum, while our observations in 

 the ovary of the guinea pig prove a much furthergoing develop- 

 ment leading to the formation of embryonal placenta and of 

 embryos in the stage of the germ layers within the ovary. It is 

 of course natural, as I emphasized on a former occasion, that 

 under these abnormal conditions the processes of development 

 cannot follow an altogether normal course, and it was therefore 



1 Leo Loeb, "On Progressive Changes in the Ova in Mammalian Ovaries, 

 Journal of Medical Research, Vol. VI., 1901. Arch.f. mikrosk. Anai., Bd. 65, 1905. 



2 H. H. Newman, Biological Bulletin, XXV., p. 52, 1913. It may be espe- 

 cially emphasized that our interpretation of the placental and embryonal structures 

 found by us in the ovaries of guinea pigs does in no way depend on the interpreta- 

 tion of those changes in the ova within the ovaries of the guinea pig which in common 

 with previous authors we held to be early abnormal segmentations of ova, while 

 a number of other investigators interpreted them as of a degenerative character. 

 There can be no doubt about the presence of further developed embryonal 

 structures in the ovaries of guinea pigs. 



