STUDIES IN MAMMALIAN EMBRYOLOGY. 527 



Fig. 15 b, — The wall of the uterus (thick red line), the non-placental 

 trophoblast and the yolk-sac in the vicinity of the mesometrium, drawn on 

 the same scale and from a similar preparation as Tigs. 15 and 15 «. 

 Fig. 15 i.— Utr. Mus. Cat. n°- Sorex 90 a, 1 r. 8 *. 



PLATE 33. 



(All these figures x 100.) 



EiG. 16. — Part of a transverse section (cf. Fig. 1) through a uterus in 

 which the blastocysts are as yet contained in the oviducts. The coiled uterine 

 glands are seen to be massed together in the antimesometrical regions. The 

 uterine lumen is more or less _L.shaped. Opposite the mesometrium the 

 uterine epithelium is much higher now than in the stages of Figs. 17 and 19. 

 Utr. Mus. Cat. n"- Sorex 124/, 3 r. 3 s. 



Fig. 17. — Part of a section through the wall of the uterus opposite the 

 mesometrium, in a later stage of pregnancy (cf. Fig. 3 and Fig. 66). The 

 epithelium is flattened consequent upon the stretching of the wall and the 

 distension of the lumen. 



Utr. Mus. Cat. n°- Sorex 2 a, 5 r, 18 *. 



Fig. 18. — Ibid., through the region where the uterine wall of the same 

 specimen is thickest (cf. Fig. 3). The epithelium has as yet not entered 

 upon any proliferating process, 



Utr. Mus. Cat, n°- Sorex 2 a, 5 r. 25 *. 



Fig. 19. — The same as Fig. 17, but of a somewhat later stage (cf. Fig. 4). 

 Proliferation of the epithelium has commenced (cf. Figs. 67 — 69). 

 Utr. Mus. Cat. no- Sorex 52 e, 3 r. 24 s. 



Fig. 20. — The same as Fig. 18, but in a stage in which the proliferation of 

 the lateral uterine epithelium is already considerable (cf. Fig. 4), This pro- 

 liferation differs in character from that of Figs. 67 — 71, there being no 

 formation of crypts. The omphaloidean trophoblast will very soon become 

 adherent against it. Blood circulates in capillary spaces between these pro- 

 liferated epithelium cells. 



Utr. Mus. Cat. n"- Sorex 52 e, 3 r. 24 s. 



Figs. 21 — 26. — Later stages of a portion of the uterine wall opposite the 

 mesometrium (cf. Figs. 4 — 9). The secondary epithelial crypts which originate 

 by the peculiar proliferation of the uterine epithelium, that commenced in 

 Fig. 19, gradually attain their full development in Figs. 25 and 26 (cf. Fig. 

 74). In the latter figure many of the crypts are not indicated because they 

 are flattened and pressed together. Maternal blood-vessels are everywhere 

 present between the crypts. In Fig. 26 the amnion is nearly complete, and 



