106 



DE VEL OPMENT. 



and locomotive system, the cutis, all the connective tissues, and the genito-urinary 

 organs with the exception of the epithelium of the bladder and urethra, which i's 



151 



FIG. 80.* Diagrams to show the development of the three blastodermic layers on antero-posterior section. A 

 Portion of ovum with the vitelline membrane and germinal area. BCD E'F. Various stages of development 

 G. Ovum in the uterus and formation of decidua. 1. Vitelline membrane. 2. External blastodermic layer. 2'. 

 Vesicula serosa. 3. Middle blastodermic layer. 4. Internal layer. 5. Vestige of the future embryo. 0. Ceph- 

 alic flexure of the amnion. 7. Caudal flexure. 8. Spot where the amnion and vesicula serosa are continuous. 

 8'. Posterior umbilicus. 9. Cardiac cavitv. 10. Splanchnopleure layer of the umbilical vesicle. 11. Somato- 

 pleure layer of the amnion. 12. Internal layer or the blastoderm forming the intestine. 13,14. External layer 

 of the placenta, extending to the inner surface of the vesicula serosa. 15. The same, now completely applied to 

 the inner surface of the vesicula serosa. 16. Umbilical cord. 17. Umbilical vessels. IS. Amnion. 19. Chorion. 

 20. Foetal placenta. 21. Mucous membrane of uterus. 22. Maternal placenta. 23. Decidua reflexa. 24. Mus- 

 cular wall of uterus. 



*The same note applies to this as to the preceding diagram. 



developed from the hypoblast. The vascular system of the foetus extends to the 

 yolk and the maternal parts along the umbilical vesicle and allantois, so that the 



