PATHOLOGIC OVA, ALBINO RAT 129 



sections of the series which includes this vesicle, which is cut 

 in very favorable longitudinal direction, and is thus readily ori- 

 ented with reference to mesometrial and antimesometrial por- 

 tion, is there seen any thickening of the outer layer of cells, to 

 form the part known as the floor of the vesicle, which at this stage 

 of development is uniformly directed toward the mesometrial 

 border. In A and B of figure 23, Part I, are shown vesicles with 

 which the ovum here discussed may be compared. In the 

 preparation under discussion, the yolk and parietal entoderm 

 form almost a continuous layer, one of the detached cells show- 

 ing a mitotic phase. In the normal vesicles of this stage of de- 

 velopment the parietal entoderm is represented by a few scat- 

 tered cells, as may be observed by a study of the figures to which 

 reference is above made. Whether this vesicle is to be regarded 

 as showing a later stage of an ovum in which there was irregu- 

 larity in the formation of the segmentation cavity, I must for the 

 present, leave as problematic. It has occurred to me that by 

 enlargement of the segmentation cavity of an ovum such as 

 shown in figure 5, with centrally placed segmentation cavity, 

 there might result in further development the formation of a 

 vesicle such as shown in B of figure 6. 



It is freely admitted that the deductions here made, relative 

 to irregularity in the formation of segmentation cavity, are not 

 supported by conclusive evidence. It has seemed to me, however, 

 that the interpretations given to the appearances presented are 

 less open to criticism than others that might be suggested. These 

 abnormal ova also suggest an inherent defect in the ova, leading 

 to abnormal development, rather than abnormal development 

 resulting from defective environment. 



DEGENERATION OF OVA AS RESULT OF PATHOLOGIC 

 UTERINE MUCOSA 



In figure 7 are reproduced two ova which seem to me to show 

 the primary stages of degeneration owing to pathologic condition 

 of the uterine mucosa. Vesicle A was taken from the uterus of 

 rat No. 91, 5 days, 16 hours, after insemination. In the uterus 

 of this rat there were found only two ova. Vesicle B was taken 



