382 G. CARL HUBER 
The causes operative in this retardation of development and 
differentiation of the ectodermal vesicle and primary embryonic 
ectoderm, | have been unable to determine. They would ap- 
pear to be inherent in the egg-cylinder, since ectoplacental cone 
and visceral entoderm, so far as may be determined from a study 
of sections, appear to have functioned normally, in furnishing the 
necessary embryotroph in the form of maternal hemoglobin, as 
is normal for egg-cylinders of the albino rat of this stage of 
development: 
TWO EGG-CYLINDERS IN ONE DECIDUAL CRYPT 
The ova portrayed in figure 10 present a condition which must be 
regarded as exceedingly rare, since it represents the only instance of 
this condition observed in the extended series of preparations of 
the various stages of the development of the albino rat from the 
end of the first to the end of the ninth day after insemination, 
in my possession. This preparation is from rat No. 87, 9 days 
after the beginning of insemination. The uterus of this rat con- 
tained, other than the preparation here considered, six egg- 
cylinders of normal development, all showing a stage which is 
slightly older than that shown in figure 31, Part I, in that the 
mesoderm shows further development than is shown in that 
figure. In the preparation here figured there are found two 
ege-cylinders enclosed within the same decidual crypt. This 
figure, which is drawn by combining the drawings made from two 
sections, is reproduced at a magnification of 150 diameters, while 
all of the other figures portraying sections of ova, both in Part 
IT and in Part IT of this communication, are reproduced at a mag- 
nification of 200 diameters. This should be borne in mind when 
comparing this figure with the others. In figure 10, the lower 
portion of the large egg-cylinder to the level of the lower end of 
the smaller one was drawn from one section, while the remainder 
of the figure was drawn from the fourth following one. The 
adjustment was made by overlapping in the camera lucida 
drawing (xX 600) the sharp mesometrial border of the primary 
embryonic ectoderm of the larger egg-cylinder. Scarcely any 
