SPOLIA NEMORIS. 115 
maternal epithelium is yet more peculiar, considering the fact 
that an uncommonly marked proliferation of this epithelium 
precedes its definite disappearance. 
Secondly, the question has been much ventilated which part 
the trophoblast plays in the attachment of the blastocyst. 
Both in Insectivora (Erinaceus, Sorex, by myself) and in 
Rodentia (rabbit, mouse, rat, Meriones, Cavia, by Duval) this 
has been fully inquired into, and overwhelming evidence has 
been forthcoming to show that this epiblastic layer and no other 
but this layer contributes in an unexpected measure to the 
genesis of the tissues that constitute the placenta. 
It may even be said that since the penetration of maternal 
blood into lacunar spaces of the hedgehog’s trophoblast that 
are devoid of any vascular endothelium has been described as 
occurring even at stages as early as the didermic blastocyst,! 
and since Duval made his first communication about the rabbit 
and other Rodents to the Paris Société de Biologie,2—communi- 
cations that have soon after been worked out in his masterly 
volume, ‘Le Placenta des Rongeurs’ ( Paris, 1889-92),—a conflict 
of opinion has arisen about the real nature of the placenta, in 
which on one side are a majority of the above-cited German 
anatomists, and on the other the two authors just named and 
also E. van Beneden with reference to the bat (*‘ Comptes 
Rendus de la Société de Biol.,’ vol. v, Novembre, 1888), and 
J. Masius, his pupil, with reference to the rabbit (I. c.). 
The question centres in the way in which the osmotic 
interchange between the maternal and the embryonic blood 
comes about, influenced as it is by preparatory processes that 
take place in those regions where the trophoblast of the 
blastocyst comes in contact with the inner lining of the uterus. 
Now this phenomenon is easy enough to understand in the 
horse, the pig, and several other mammals on which the 
1 Hubrecht, ‘Kleimblatterbildung und Placentation des Igels,” ‘ Ver- 
handlungen der Anat. Gesellsch.; Versammlung zu Wirzburg,’ Mai, 1888 ; 
‘Anat. Anz.,’ ili, p.512; and ‘‘ The Placentation of Hrinaceus europeus,” 
‘Quart. Journ. Micr. Sci.,’ vol. xxx. 
2 *Comptes-rendus de la Société de Biologie,’ Mars et Juillet, 1887; 
Octobre et Novembre, 1888, vols. iv et y. 
