24 G. CARL HUBER 



stage of the mouse, given by Sobotta and Melissinos, the nuclei 

 of the two cells lie in about their center and essentially in the 

 same plane. In my own material of the 2-cell stage of the albino 

 rat it is not unusual to find the nuclei of the respective cells 

 nearer the opposite poles of the two cells than at their centers, 

 as shown in C, of figure 1. In B of this figure, where the two 

 nuclei appear as lying much nearer the center of the cells, 

 they are in reality placed much as in C, as is shown by .the 

 reconstruction. 



Fig. 7 Model of the right oviduct of rat No. 59, 2 days. X 10. Not quite the 

 entire oviduct was available for reconstruction, the upper end of the uterine 

 horn thus not shown in the figure. The position of the four 2-cell stages, each 

 of which is outlined in a circle, found within the tube, is shown as if seen through 

 a transparent wall. 



To determine the position of the segmented ovum in the 

 2-cell stage in the oviduct, reconstructions were made of two 

 oviducts. In figure 7 is shown a reconstruction of the right 

 oviduct of rat No. 59, killed two days after the beginning of 

 insemination. In preparing the material for embedding, this 

 oviduct was cut not quite at its insertion into the uterine horn. 

 The portion of the oviduct reconstructed measures 2.29 cm. 

 Nine major loops are shown. The four ova in the 2-cell stage 

 found in this tube are situated in the sixth to the seventh loop 

 at a distance of about 1.4 cm. from the fimbriated end. This 

 portion of the oviduct falls to segment three of Sobotta' s designa- 

 tion. It is lined by non-ciliated epithelium resting on a mucosa 

 with inconspicuous secondary folds, but presenting four or five 

 characteristic major folds. This portion of the oviduct is closely 



