aoe G. CARL HUBER 
Sobotta’s statement concerning this point, which, owing to its 
importance, I quote in full, reads as follows: 
Man wird diese mikroskopisch erkennbaren Verhiltnisse nicht an- 
ders deuten kénnen als in folgender Weise: Die Himoglobinschollen, 
die durch die éussere Wand des Dottersackes in die Dottersackhéhle 
gelangt sind, werden von der Oberflaiche des zylindrischen, die ganze 
Seitenfliche des Eizylinders itiberziehenden visceralen Dottersack- 
epithels aus resorbiert und zwar geschieht das in der Weise, dass die 
Himoglobinschollen ziinachst als solehe in der Zelle selbst eintreten, 
dann aber im vacuolisierten Teil der Zelle gleichsam verdaut werden, 
wobei die einzelnen kleinen Schollen vorher zu grésseren Tropfen zusam- 
men-fliessen scheinen. 
My own observations on the albino rat as concerns this phe- 
nomenon, more particularly as concerns the structure of the 
cells of the visceral entoderm in the region of the extraembryonic 
ectoderm, corroborate Sobotta in many particulars. This 
question will beagain and more fully considered in a contemplated 
later publication dealing with the implantation and decidua 
formation in the albino rat. It could not be considered now 
without a discussion of the changes involved in the development 
of the decidua, a question which I am not prepared to consider 
fully now. It may be stated, however, that judging from my 
own preparations and the figures of Grosser, the extravasation 
of blood into the egg chamber is not nearly so extensive in the 
albino rat as is shown in the figures of Sobotta for the mouse. 
The thin membrane which surrounds the yolk-sac cavity, 
which I have designated as the parietal or transitory ectoderm, 
is derived in development from the parietal or transitory ecto- 
derm, and the relatively few parietal entodermal cells, as de- 
scribed and figured for younger stages. At the stage of egg-cylin- 
der development under consideration—with continuous pro- 
amniotic cavity—this structure appears as a thin, practically 
homogeneous membrane with scattered, flattened nucleated 
cells on its inner surface. Sobctta regards these cells as derived 
from the parietal entoderm, the cells of the parietal ectoderm 
having disappeared. As concerns this, I am unable to speak 
with certainty, since the Congo red solution used as a double 
stain is not particularly favorable in differentially coloring these 
