440 JAS. P. HILL. 



oiuphalopleure. viL a. Vitelliue artery, vit. v. Vitelline veiu. y. spl. lu- 

 vaginated yolk splaachuopleure. 



N.B. — Unless otlierwise stated, sections are transverse. 



Tig. 1. — Wall of non-gravid uterus, Perameles. s. Serosa, m. Mucosa. 

 ep. Uterine epithelium, x 55. 



Stage A. 

 Fig. 2. — Portion of the syncytium, showing the numerous nuclei in a 

 continuous protoplasmic layer, X 740. 



Stage B. 



Fig. 3. — Portion of left uterine VFall (serosa not shown). ?«. c. Capillary 

 ofcoriuui. X 55. 



Fig. 4. — Portion of the uterine syncytium, showing tiie lobular character of 

 its deeper surface (si/n. I.), the arrangement of the nuclei, and tlie presence 

 in it of maternal capillaries {si/7i.c.). I. Leucocytes, m. c. Capillary of corium. 

 X 40. 



Stage C. 



Fig. 5. — 7 mm. embryo, P. nasuta, all. s. Allantoic stalk, y. s. Yolk- 

 stalk. X about 8. 



Fig. 6. — Section passing through the margin of the allantoic placental 

 area, and including the whole breadth of the vascular omphalopleure {vase, 

 omph.) on one side, and a portion of the bilaminar omphalopleure {bil. omph.), 

 together with the adjacent syncytium [ex. spi.). y. s. Cavity of yolk-sac. 

 X 118. 



Fig. 7. — Section of marginal portion of the allantoic placental area, x 140. 



Fig. 8. — Portion of allantoic placental area centrally from Fig. 7, showing 

 the chorionic ectoderm (ch. ect.) as a continuous layer of enlarged cells ad- 

 herent to the syncytium {pi. syn.), as in Fig. 7. X 140. 



Fig. 9. — Portion of the central region of the allantoic placental area, show- 

 ing degeneration of the chorionic ectoderm {ch. ect.) X 230. 



Fig. 10. — Section of allantoic stalk. X 140. 



Fig. 11, — Section passing through opening of allantoic canal {o. all. cl.) 

 into vesicular portion of allantois. X 118. 



Fig. 12. — Portion of the bilaminar omphalopleure in section, x 220. 



Stage D. 



Fig. 13. — Right uterus opened up, showing embryo still partially enclosed 

 in its membranes and in relation to the allantoic placental area {pi. a.). For 

 description see text (pp, 411, 412), X about 65. 



Fig, 14, — Section through the persistent portion of the proamnion, amn. 

 amnion. X 140. 



