SPOLIA NEMORIS. Ti 
experiment may still further drive home what is meant by the 
non-homology of the two cases of holoblastic segmentation and 
of the cavities which arise in these two cases inside the mono- 
dermic vesicles. 
New and valid reasons are thus accumulated for designating 
the outer layer of precociously segregated epiblast-cells that 
form the wall of this vesicle by a separate name, which at the 
same time gives expression to the consideration that adaptation 
to nutritive conditions of an entirely novel nature has initiated 
this phenomenon of precocious segregation, simultaneously 
with the diminution and the final disappearance of food-yolk, 
a phenomenon that was consequent upon the passage from the 
Hypotherian to the Eutherian stage. 
Already in 1888! have I proposed—and several embryologists, 
Dr. Robinson included, have since accepted—the name of 
trophoblast for this outer layer of the mammalian blastocyst. 
Only lately? I have given a fuller definition of the term, 
which is, however, only in one respect an amplification of the 
original definition of 1888. Then already (‘ Anat. Anz.,’ iii, 
510), I remarked that to the trophoblast belonged all those 
peculiar cellular structures of the mammalian blastocyst which 
had been indicated by different authors as Reichert’s cells and 
Rauber’s “ Deckschicht ” (Kolliker), as “ Trager ”’ (Selenka), 
Ektodermawulst (Kolliker), horseshoe-shaped proliferation 
(van Beneden). To this list may yet be added Duval’s 
** formation ectoplacentaire.” 
The amplification of 1893 just alluded to was this, that I 
not only defined the trophoblast as “ the epiblast of the mam- 
malian blastocyst that does not take part in the formation of 
the embryo,” but that I added to this, “ or of the inner lining 
of the amnion cavity.” 
The difference which obtains between the trophoblast and 
between the embryonic epiblast contributing to the formation 
of the embryo and of that inner lining of the amnion cavity, is 
1 « Anatomischer Anzeiger,’ July, 1888, p. 510. 
_? © Proces-verb. van de Kon. Akad. van Wetenschappen te Amsterdam,’ 27 
Mei, 1898, 
