42 



G. CARL HUBER 



and 3-cell stages were obtained from the upper end of the uterine 

 horn. The presence of 2-cell stages in the uterine horn has also 

 been noted by Keibel, in Erinaceus europaeus, by Van Beneden 

 in the bat, and by Hubrecht in the insectivor Tupaya javanica. 

 Finally, it may be noted that according to the observations of 

 Bischoff, the segmenting ovum of the dog occupies 8 to 10 days 

 after insemination in transit through the oviduct. 



COMPLETION OF SEGMENTATION AND BLASTODERM 1C 

 VESICLE FORMATION 



The material covering the end stages of segmentation and the 

 early stages of blastodermic vesicle formation is listed in table 5. 



TABLE 5 



Early stage of blastodermic vesicle formation 

 Morula, beginning of segmentation cavity, early 



stage of blastodermic vesicle 

 Early stage of blastodermic vesicle 

 Early stage of blastodermic vesicle 

 Early stage of blastodermic vesicle 

 Early stage of blastodermic vesicle 



Thus there are at hand 30 ova, showing late morula stages, 

 the beginning of segmentation cavity formation and early 

 stages of the blastodermic vesicle, falling in the latter half of 

 the fifth day after the beginning of insemination. In all of 

 the uteri from which this material was taken, the ova are spaced 

 in the uterine horns about as in later stages of development ; they 

 lie free in the uterine lumen, are in the main ovoid in form, their 

 long axis presenting no definite relation to the long axis of the 

 uterine horn. In preparing this material for sectioning, it was 

 the custom to cut an entire uterine horn into segments measur- 

 ing about 1.0 cm. to 1.5 cm. in length. These segments were 

 then embedded so as to admit cutting longitudinally and in a 

 plane parallel to the plane of the mesometrium. Cut in this 

 way, the majority of the ova were cut longitudinally or nearly 

 so, others in an oblique plane, others again, crosswise. Since it 



