376 Maximilian Herzog. 



The ectoderm cells of the amnion are in general of the same de- 

 scription as the shield ectoderm cells; however, they have smaller 

 protoplasmic bodies, which are not cuboidal, but rather elon- 

 gated. 



The mesoderm cells of the embryonic shield have generally oval 

 nuclei and exceedingly little protoplasm ; they are connected with 

 each other by very thin, filamentous, bipolar processes. The yolk 

 sac and amnion mesoderm cells are elongated and connected with 

 each other by bipolar processes. But where the mesoderm cells are 

 most numerous, namely, at the allantoic stalk, their nuclei are 

 larger and their protoplasm, which is fairly abundant, is generally 

 irregularly polygonal. 



The entoderm cells of the shield have nuclei very much like the 

 ectoderm cells, but the protoplasmic bodies are smaller and often 

 somewhat elongated. These cells are likewise more or less con- 

 nected with each other by bipolar though shorter and coarser pro- 

 cesses. The entoderm cells of the yolk sac have rather small nuclei, 

 rich in chromatin, and, Avhere they can be seen at their best, are 

 almost geometrically cuboidal. They are rather small in size in 

 comparison with the shield ectoderm cells. The entoderm cells of the 

 allantois are like those of the yolk sac. 



Description of Chorion and Decidua. 



Nomenclature. 



In order to facilitate the description of the chorion and of the 

 decidua in which it was found embedded, as well as to avoid any 

 misunderstanding on the part of the reader, it is well to outline 

 shortly the nomenclature used. 



That part of the uterine decidua on which the inner pole of the 

 ovum rests and which is characterized in our case by the presence 

 of large cystic gland spaces and lacunae, densely crowded with 

 blood, we will call the decidua hasalis. That thin strip of decidual 

 tissue which separates the ovum from the uterine cavity will be desig- 

 nated as decidua capsularis, and that part of the decidua surrounding 

 on all sides the equator of the ovum we will call the decidua vera. 



