138 G. CARL HUBER 



The causes operative in this retardation of development and 

 differentiation of the ectodermal vesicle and primary embryonic 

 ectoderm, I 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-CYLIXDERS 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 

 egg-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 

 I and in Part II 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 ( X 600) the sharp mesometrial border of the primary 

 embryonic ectoderm of the larger egg-cylinder. Scarcely any 



