^5g MOUSE EMBRYO 



THE MOUSE EMBRYO: 6.5 TO 14.5 DAYS POST-CONCEPTION 



Fig. 33 - Mouse embryo at 6. 5 days showing relation to sur- 

 rounding uterine epithelium. Note breakdown of 

 adjacent uterine tissue. 



Fig. 34 - Section distinguishing between inner solid ectoderm 

 and outer flocculent-type endoderm. 



Fig. 35 - Thickening of inner ectoderm of the head process, 

 at 6. 5 days. 



Fig. 36 - Section through uterus at level of 7. 5 day embryo 

 showing extent of uterine involvement. Ectopla- 

 cental cone is solid mass toward center of section. 



Fig. 37 - Transverse section through more posterior level of 



embryo showing exocoelom and two portions of pro- 

 amniotic cavity. 



Fig. 38 - Longitudinal section at about 7.0 days showing first 

 appearance of all three germ layers. 



Fig. 39 - Longitudinal (sagittal) section at 7.5 days showing 

 all structures from ectoplacental cone (above) to 

 head process (below). 



Fig. 40 - Mouse embryo at 8. 5 days. Note earliest neural 

 invagination to form the central nervous system in 

 inner thick ectoderm. Section through entire 

 uterus at this level. 



Fig. 41 - Enlarged view of 8.5 day embryo showing earliest 

 neural differentiation. 



Fig. 42 - Embryo at 8. 5 days showing amniotic membrane 

 across center of embryo, saccular allantois above 

 and to the left, ectoplacental cavity' slit-like and 

 above, large amniotic cavity (below) with early 

 differentiation of the primary neural axis (thicken- 

 ing below). 



Fig. 43 - Transverse section through early head structures at 

 9. 5 days showing two dorsal and two ventral aortae 

 and enclosed lateral coelomic spaces. Archenteron 

 is the central cavity above which is the notochord 

 and the closed neural tube. Easily compared with 

 frog, chick or any other mammal. 



Fig. 44 - Section at 10,5 days of the head process level with 

 brain ectoderm still unclosed, but with notochord 

 and archenteron distinct. 



Fig. 45 - Section of eye at 12. 5 days development, at level 

 of origin of the optic nerve. Note state of develop- 

 ment of the lens, cornea and retina. 



Fig. 46 - Eye of the mouse embryo at 14. 5 days showing con- 

 siderable further development beyond that of fig. 45. 



