MOVEMENTS AND FOLDINGS 



INNER CELL 

 MASS 



57 



ENDODERM 



TROPHOBLAST 

 ECTODERM 



Fig. 15. — The development of the rabbit, {a) and {b) are sections through 

 the whole egg showing the formation of the endoderm, {c) is a surface 

 view of the primitive streak which develops on the inner cell mass, and 

 (d) (from Quain's Anatorny) is a much later stage showing the gill slits 



