380 A. A. W. HUBRECHT. 
blastocyst is said to lie loosely in its cavity, and at the same 
time of the fact that no human subject has yet been examined 
in the same conditions of freshness in which I had always 
been able to obtain the hedgehogs, but rather in the conditions 
of the specimen which yielded these different results, or even 
in still less favorable conditions. 
This necessarily leads to the suggestion whether the loose 
attachment of the human blastocyst must not be considered to 
be an artefact, and whether it is not more probable that here 
too blastocyst and trophosphere are much more intimately 
fused in the live and fresh condition. 
The way in which this fusion may be effected can a fortiori 
only be discussed for the present in a very speculative way. 
Still, now that we have seen that the ripe placenta of man and 
hedgehog offer many unexpected points of comparison, it is 
only natural to infer that the very early stages may also cor- 
respond in several respects. One of the first propositions we 
would then be Jed to would be this: Must not the early ecto- 
dermal villi be looked upon in the same light as the villi on 
the hedgehog’s blastocyst (cf. Pl. XVI, figs. 14—20)? And 
can they not have arisen in asimilar way, not so much as active 
outgrowths, but as remnants from the stage in which a thicker 
trophoblast acquired lacunze which enter into communication 
with maternal blood-cavities, such as figs. 14 and 39 illustrate ? 
This would go far to explain the profuseness of trophoblastic 
villi in so early a stage as the so-called Reichert’s ovum. In 
that case a maternal trophospongia, in the shape of a hollow 
sphere, might be expected to be present, and to contain spa- 
cious blood-lacune that gradually become obliterated during 
the metamorphosis of the decidua reflexa into a membrana- 
ceous layer, and its fusion with the decidua vera. 
The villi in this region disappear, and the chorion lve 
comes into existence, whereas in the region of the chorion 
frondosum the more intimate connection between tropho- 
blastic and maternal tissue persists, and the trophospheric 
lacunee may develop into those of the placenta. Such is the 
general developmental course which may prove applicable to 
