404 A. A. W. HUBRECHT. 
PLATE XXVI. 
Fig. 55. Later stage enlarged on same scale. The trophoblast has again 
become considerably thicker, the blood-spaces in it having at the 
same time increased. Z's.,a.v., sp., all., and hy. a. as in Fig. 54. 
e. bl, Embryonic blood-corpuscles. m. 4/. Maternal blood-corpuscles. 
v. Larger adherent blood-vessel in the allantois. The allantoic 
villi are in this stage partly surrounded by a pseudo-epithelium derived 
from the adjacent trophoblast, which was already more or less indicated 
in Fig. 54. (Mus. Utr. Cat. no Erin. 54 51, 14 s.) 
Fig. 56. Still later stage, same scale. Letters as in Fig. 55. The 
allantoic villi may here be said to be bathed on all sides by maternal 
blood, circulating in spacious lacune that are sustained by trophoblastic 
(embryonic) tissue. (Mus. Utr. Cat. no Erin, 18 d, 2 s.) 
PLATE XXVII. 
Fig. 57. Vertical section through a portion of the ripe placenta of 
Erinaceus. The region a is that which in the preceding figures was 
called the trophospongia. The region 4 corresponds to the combined 
trophoblast and allantois. Further outwards (in casu upwards) of 
the former is the proliferated mucosa, which has been flattened out to 
a cup-shape (ef. diagram Fig. 36), but of which in this figure hardly 
anything is represented. Between it and the trophospongia remnants 
of the deciduofracts can be observed. They are marked dd. The 
blood-spaces in the trophospongia have yet increased in size, although 
the trophospongia as such is relatively considerably reduced when 
compared to trophoblast and allantois. To suit the size of the Plate 
the latter region (4) is in this figure even too restricted, and generally 
exceeds the trophospongia in size still more considerably than is here 
indicated. In the region of letter ¢ remnants of the layer of fusiform 
cells between trophospongia and trophoblast are distinctly seen. The 
trophoblast tissue is seen to be really soaked with maternal blood, and 
at the same time most intimately and indivisibly united with the 
allantois tissue. The latter can yet at different points be recognised, 
and towards the cavity of the allantois larger arteries (all. art.) are 
seen in transverse sections. The smaller arteries are seen to rise 
radially into the trophoblastic tissue, and reach upwards to close 
towards the trophospongia. For the genetic evolution of the spaces 
(sp.), &e., see the foregoing Figs. 39, 42, 52—56. (Mus. Utr. Cat. 
n® Erin, 209 a—a’.) 
