36 G. CARL HUBER 



cavity, just distal to the opening of the oviduct, lying free in a 

 slightly distended portion of the lumen. This morula is of 

 irregular discoidal form, presenting an appearance which sug- 

 gests that it was fixed soon after it escaped from the oviduct. A 

 fifth morula, of regular oval form, comprising very probably 18 

 cells, all of which present resting nuclei, is lodged in a shallow 

 pit of the uterine mucosa a little over 1 cm. from the tubal open- 

 ing. This portion of the uterine horn was not included in the 

 reconstruction, the position of this morula is not, therefore, in- 

 dicated in the figure. It is evident that this tube was fixed while 

 the several morula masses were in transit from the oviduct to 

 the uterine horn, which occurs, to judge from the material at 

 my disposal, at the end of the fourth day after the beginning 

 of insemination. The morula masses of the right tube are sit- 

 uated in the oviduct just before its point of insertion into the 

 uterine horn, in about the same relative position as are the 

 three upper morula masses of the left side, as shown in the re- 

 construction. They are of discoidal form, in close relation and 

 appear to comprise, the one 12, the other two 14 to 16 cells. In 

 B, C and D of figure 19 are reproduced sections of each of these 

 three morula stages. The figures, however, are delusive in that 

 the section for each passes through the greatest diameters of the 

 respective morula. 



The material at hand permits the conclusion that in the 

 albino rat the segmenting ova pass from the oviduct to the 

 uterine horn at the end of the fourth day after the beginning 

 of insemination, probably in the 12-cell to 16-cell stages. With 

 the beginning of the fifth day, as will appear from further dis- 

 cussion, all of the ova are to be found in the uterine horn. 



SUMMARY OF SEGMENTATION STAGES, RATE, AND VOLUME 



CHANGES 



The following summary of the data (table 3) gained by a study 

 of the models of oviducts containing ova in stages from the pro- 

 nuclear to 12-cell to 16-cell stages in which latter stage transit 

 to the uterine horn occurs, is presented to indicate rate of 

 transit within the oviduct. The regularity of the rate of transit 



