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G. CARL HUBER 



be projected with any degree of certainty. The most charac- 

 teristic vesicle showing this phenomenon is presented in figure 3, 

 and is taken from rat No 53, 5 days after insemination, the 

 uterus of which contained seven blastodermic vesicles showing- 

 early stages of development, four of which are reproduced in 

 figure 22, Part I. In A and B of figure 3 are reproduced two 

 consecutive sections of a series of five sections of 10 m thickness, 

 includ'ng this ovum. In the lower part of this ovum there is 

 found a small segmentation cavity, bounded by cells which 

 present normal appearances. The roof of this vesicle is slightly 



Fiy;- 3 Early stages of the blastodermic vesicle of the albino rat, presenting 

 evidence of irregular or re1 arded segmentation. X 200. Rat No. 53, 5 days after 

 the beginning of insemination. 



Fig. 4 Three ova of the albino ral . showing early blastodermic vesicle stages, 

 in each of which certain of the cells suggesl irregular or retarded segmentation. 

 X 200. A. rat No. ill. I days, I I hours, after the beginning of insemination. B, 

 rat No. (is. 4 days. I") hours, after the beginning of insemination. C, rat No. 

 54, 6 days, 16 hours, after the beginning of insemination. 



folded and compressed, as a consequence of which the roof wall 

 in the sections figured is presented in part as seen in surface 

 view. In the floor of this vesicle there is to be observed, sur- 

 rounded by other smaller cells, one large cell, of nearly spherical 

 shape, having a diameter which is three or four times as great 

 as that of the majority of the surrounding cells. The protoplasm 

 of this large cell stains less deeply than does that of the majority 

 of the other cells constituting the floor of the vesicle. Its nu- 

 cleus is relatively large and slightly lobulated, so much so that in 

 the section of it shown in A of this figure, in the optical section 

 sketched, the nucleus appears as three separate nuclei, in reality, 



