534 A. A. W. HUBEECHT. 



PLATE 37. 



rig. so X 200. All the other figures x 260. Both the maternal and the 

 embryouic blood-corpuscles are coloured red on this Plate. 



Fig. 74. — Part of a section through the future placentary region when 

 the proliferation of the maternal epithelium, which precedes the adhesion 

 of the blastocyst, has attained its maximum of development. The crypts 

 reach through the whole thickness of the proliferation (cf. Figs. 6 and 24). 

 Utr. Mus. Cat. n°- Sorex 45 c, 3 r. 17 s. 



Fig. 75. — One of the proliferating knobs of allantoidean trophoblast 

 penetrating into the mouth of a secondary epithelial crypt in the future 

 placentary region. Large nuclei reveal other epithelial crypts tangentially 

 cut (cf. Figs. 8 and 9). 



Utr. Mus. Cat. n°- Sorex 51 e, 2 r. 8 s. 

 Fig. 76 — 79. — Four different portions of the allantoidean trophoblast 

 before its adhesion against the maternal tissue. In all — but most especially 

 in Fig. 79 — the differentiation of cytoblast and plasmodiblast has commenced. 



Li Fig 76 the amnion is just being completed. 



In Figs. 78 and 79 distinct and massive trophoblastic knobs are re- 

 presented. 



Fig. 76.— Utr. Mus. Cat. n'*- Sorex 106 e, 2 r. 19 s. 



Fig. 77.— „ „ 51 a, 2 r. 24 s. 



Fig. 78.— „ „ 51 c, 5 r. 20 s. 



Fig. 79.— „ „ 106/, 4 r. 15 *. 



Fig. 80. — A similar section to that of Fig. 28 (cf. also Fig. 11), more con- 

 siderably enlarged. The allantoidean trophoblast and its protuberances have 

 become fused with the maternal tissue, and have further proliferated under 

 partial destruction of the latter. The trophoblastic knobs are being hollowed 

 out, allantoidean villi penetrating into the cavities thus originating. The 

 differentiation of plasmodiblast between the protuberances has commenced. 



Utr. Mus. Cat. n°- Sorex 3 S, 2, 1 r. 17 s. 



Fig. 81. — Part of the placentary region of Fig. 12, more considerably 

 enlarged. The upper half of the figure represents maternal tissue (secon- 

 dary epithelial crypts, with blood capillaries between them), the lower half 

 trophoblastic tissue. Below this is the allantois, with a distended blood- 

 vessel and two villi. The trophoblast is subdivided in a more deeply stained 

 cytoblast (which is the superficial layer, and which visibly ensheathes the 

 villi) and an intervening mass of cells (plasmodiblast) in which the maternal 

 blood circulates. In this figure these two have been torn asunder in the 

 lower part of the figure ; in more normal circumstances they firmly adhere 

 together. The exact boundary line between the " plasmodiblast " and the 

 maternal tissue cannot be distinctly indicated ; it takes its course somewhere 



