46 G. CARL HUBER 



uterine epithelium presented a ciliary border, present even in 

 the shallow pit lodging the ovum sketched. He argues from this 

 that the shallow depression and the flattening of the epithelium 

 are not a result of pressure exerted by the vesicle, as thought by 

 Sobotta and Melissinos, but must be due to an active change in 

 the epithelium itself. The mucosa underlying the shallow pits 

 presents at this stage no change of structure. I am thus in ac- 

 cord with Widakowich when he states that he was not able to 

 observe in the mucosa of the rat in the early stages of gravidity, 

 the giant cells described by Disse as found in the uterine mucosa 

 of Arvicola arvilis, in similar stages. 



The form presented by the ova of the albino rat, in the late 

 morula stages and the early stages of blastodermic vesicle, is 

 ovoid, as may be seen from the figures to be presented. Wida- 

 kowich is inclined to believe that the form of the blastodermic 

 vesicle of the rat is in a measure dependent on the general form 

 of the space in which it is lodged. He figures two vesicles (figs. 

 1-2) one of which is nearly spherical, the other of distinctly oval 

 form. Duval (figs. 73-83) presents vesicles having ovoid, trian- 

 gular, and spherical forms. Christiani's figures covering these 

 stages, are too schematic to be of any value in drawing con- 

 clusions. I fear Robinson's account is based on imperfectly 

 fixed material. He states that "toward the end of the fifth day, 

 or the commencement of the sixth day, the longitudinal axis 

 of the blastodermic vesicle is 125 /j. long. During the sixth 

 day, that axis is diminished, first to 95 M, and then to 64 //, after 

 which it again increases, and at the commencement of the seventh 

 day, it is 121 /*." Neither Fraser nor Selenka describes nor fig- 

 ures the stages here considered. In the mouse, according to 

 the accounts of Melissinos, Burckhard, and Sobotta, the form of 

 the blastodermic vesicle in early stages is spherical. 



The more specific consideration of my own material I shall 

 introduce with a discussion of three stages taken from the uterus 

 of rat No. 52, killed 4 days, 15 hours after the beginning of 

 insemination. In A, of figure 20, there is reproduced the mid- 

 dle one of seven sections of a late morula stage. This morula 

 is of ovoid form, measuring 85 /j. in its long diameter, 54 /x in its 



