176 RICHARD ASSHETON. 



the pressure which now is applied to the vesicle from without 

 by reason of the resistance offered by the elasticity of the walls 

 of the uterus to the internal hydrostatic pressure. 



Pirst of all, let us consider what is the nature of these 

 papilla-like growths. 



Sometimes during the eighth day, it may certainly be as 

 early as the seventh day four hours, when the uterus is swollen 

 very considerably by the pressure of the contained blastodermic 

 vesicle, here and there it may be noticed in transverse sec- 

 tion that over all the lower surface of the vesicle certain of 

 the epiblast cells are no longer so much flattened, but the 

 nuclei appear rounded instead of oval in section, and the proto- 

 plasmic part of the cell much more distinct and granular — 

 altogether more comfortable-looking (v. a., fig. 5). A little 

 further along, at b., may be seen a couple of such nuclei in a 

 mass of granular protoplasm. At c. a group of three or four, 

 or more, of such nuclei in a mass of granular protoplasm. 

 Outside this may be seen the torn remnants of the much 

 attenuated albumen layer. The portion of the walls of the 

 vesicle here figured was part of the lower pole of the blasto- 

 dermic vesicle of an embryo of seven days four hours. Al- 

 though I did not succeed in taking it out of its place in the 

 uterus unhurt, it was, nevertheless, not yet attached to the 

 walls of the uterus at any point. It may be noted that here 

 there is no trace of an inner layer or hypoblast. 



In fig. 6, another piece of the wall of a vesicle of about the 

 same age cut in situ in the uterus, this piece shows a por- 

 tion of the side of the blastodermic vesicle, or, at any rate, a 

 portion not so far removed from the embryonic pole as that 

 drawn in fig. 5. Here in fig. 6 the same features are to be 

 seen in the epiblast as described for fig. 5. There is here, how- 

 ever, a well-developed hypoblastic layer. 



Fig. 8 is a section of the upper part of the wall of the vesicle, 

 of that part which closely adjoins the embryonic disc. This 

 specimen is from an embryo from the same rabbit as that 

 from which fig. 5 was drawn, and almost exactly the same 

 size. Here it will be noticed that not only are the cells 



