SPOLIA NEMORIS. 113 
very active proliferating processes preparatory to the placentary 
fixation of the blastocyst, whereas in my former papers I have 
described the same activity for Erinaceus! and Sorex.* 
Robinson’s speculations having tended to bring the part that 
the hypoblast plays in the mammalian blastocyst more into 
prominence, E. van Beneden has, on the contrary, upheld® that 
the inner layer—his “so-called” hypoblast—of the mam- 
malian blastocyst is not homologous with the hypoblast of 
Amphioxus, but should be regarded as a yolk-envelope and be 
no longer designated by the name of hypoblast, but by that of 
lecithophore. 
These views, tentatively accepted by Rabl,* have been com- 
bated by Keibel,> by myself,® and by others. Also with 
respect to this question I have no doubt that the material here 
described will furnish very useful and perhaps decisive data. 
Decisive, for example, with respect to the question whether 
mesoblast takes its origin out of this hypoblast layer (v. 
Beneden’s lecitophore), as Bonnet? and Hubrecht® have dis- 
tinctly stated and figured it to do, although others (Keibel,® for 
instance) deny this. It is clear that such participation in the 
formation of the mesoblast is in itself sufficient to invalidate 
v. Beneden’s considerations about the “lecitophore” and to 
establish the homology of this layer with the hypoblast of 
Amphioxus and the lower Vertebrates. 
I have myself tried to explain the peculiarities that in mam- 
mals also attend the formation of the hypoblast by the sugges- 
' «Quart. Journ. Micr. Sci.,’ vol. xxx. 
2 Thid., vol. xxxi. 
3 * Anatomischer Anzeiger,’ ili, p. 713. 
4 « Theorie des Mesoderms,” ‘ Morphol. Jahrb.,’ Bd. xv. 
° “Zur Entwickelungsgesch. der Chorda bei den Saugern,” ‘ Archiv fur 
Anat. und Physiol. Anat.,’ Abth., 1889. 
6 «Development of the Germinal Layers of Sorex vulgaris,” ‘Quart. 
Journ. Micr. Sci.,’ vol. xxxi, 1890. 
7 © Beitrige z. Embryologie d. Wiederkauer,” 1 und 2, ‘ Archiv fiir Anat. 
und Physiol.,’ Anat. Abth., 1884, p. 170, and 1889. 
S “Ueber die Entwickelungsgesch. des Schweines,” ‘ Anat. Anz.,’ vi, 1891, 
and Schwalbe’s ‘Morph. Arbeiten,’ Bd. ili, 1893, S. 69. 
VoL. 36, PART 1.—NEW SER. H 
