290 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 » long. During the sixth 
day, that axis is diminished, first to 95 uw, and then to 64 u, 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, Burekhard, 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 u in its long diameter, 54 u» in its 
