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 ol the cndoderm, (c) is a surface 

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

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



