128 G. CARL HTJBER 



this uterus. I am for the present unable to offer any plausible 

 explanation or give reasons for such abnormal development of the 

 segmentation cavity. The fate of such a structure may perhaps 

 be conjectured from a study of the abnormal ovum shown in A 

 of figure 6, interpreted as showing a similar abnormality, but ob- 

 tained in early stages of degeneration. This ovum and that 

 shown in B of the same figure was obtained from the uterus of 

 rat No. 90, 6 days, 17 hours, after insemination. In the uterus 

 of this rat there are found six ova, only one of which was de- 

 veloped to a stage comparable to that shown in figure 24 (Part 

 I) of about the same age. Three other vesicles present a slightly 

 younger stage and may be compared with vesicles shown in 

 D and E of figure 23, Part I. None of these four vesicles is 

 favorably cut, but so far as may be determined, are of normal 

 structure for the respective stages represented. A of figure 6 

 is also cut slightly obliquely, not sufficiently so, however, to 

 make difficult its interpretation. The figure drawn is that of 

 the third of a series of seven sections having 10 ^ thickness, and 

 depicts what is regarded as representing an ovum with abnormal 

 segmentation cavity formation. In this ovum, the segmentation 

 cavity is slightly more eccentric than is that shown in figure 5, 

 and contains a granular detritus which in the preparations is 

 distinctly stained with Congo red. The roof of this vesicle is 

 composed almost throughout of more than one layer of cells. 

 There is no differentiation of ectoplacental cone and ectodermal 

 node, nor of yolk entoderm. Two cells regarded as phagocytic 

 leucocytes, staining much more deeply in Congo red than do the 

 cells of the ovum, have, in the section figured, penetrated the 

 egg-mass, indicating early degenerative changes. 



The vesicle shown in B of figure 6, obtained from the same rat, 

 is favorably cut, and is readily followed through the series. The 

 structural appearance presented by this vesicle is not explained by 

 supposing it due to very oblique plane of section of a normal 

 vesicle, a plane of section which might include the roof of the 

 vesicle while avoiding its floor. The vesicle is abnormal in that 

 it presents a want of development of the thickened germ disc, 

 and a hyperdevelopment of the yolk entoderm. In none of the 



