106 A. A. W. HUBRECHT. 
very pressing grounds which have already been discussed in 
preceding chapters, the proliferation of the trophoblast only 
takes place on a restricted portion of the spherical surface of 
the trophoblast, as I have demonstrated elsewhere (94 B, 796, 
99). It is by this restricted portion that the blastocyst first 
adheres to the maternal uterine epithelium, and it is here 
that proliferations arise which become fused with other pro- 
liferations of the maternal trophospongia in a way analogous 
to what we noticed for the hedgehog. ‘Thus a vascular 
spongework is brought about, against which the developing 
placenta comes to be attached (Figs. 147, 150). The details 
of the trophoblastic differentiation of Tarsius I have described 
in my former paper (’99); it may here suffice to say that 
besides the development of lacunez and large giant-cells with 
very peculiar nuclei, | have noticed an interesting phenomenon 
in these trophoblastic and also in maternal trophospongian 
cells. 
This phenomenon, which will have to be inquired into also 
in other mammals, consists in the production of red blood- 
corpuscles out of these cells, or rather out of the nuclear 
matter, which undergoes a series of most remarkable changes 
and transformations. ‘Those red blood-corpuscles, devoid of 
a nucleus, would thus be derived from nuclear matter of 
certain trophoblast cells. his is certainly less astonishing, 
since it has been shown by me in a former paper (799) that 
the definite red blood-corpuscles of the embryo also arise by 
nuclear transformation in the nucleated blood-mother-cells. 
The production of blood-corpuscles by the cells of a larval 
envelope is surely an unexpected histological phenomenon. 
Still, the details of differential segregation during the succes- 
sive stages of cell lineage are not yet well enough known to 
justify any apodictic negation. The possibility is not ex- 
cluded that at the first cleavage (suppose this to separate 
trophoblast from embryonic knob) certain potentialities of 
hematogenesis may be passed on to this trophoblast mother- 
cell. 
Besides the cases of trophoblastic proliferation, preparatory 
