icm 



32 



Fig. 31 Section through the trunk region of a seventy-two hour embryo 

 without a circulation; Experiment A, 1913. The extreme anterior end of the 

 intermediate cell mass, icm, is represented by deeper staining cells between the 

 notocord and intestine, Int; the primary kidney ducts, WD, are lateral to the mass. 



Fig. 32 Represents a more posterior section through the same embryo; 

 in this region the intermediate cell mass, icm, is more extensive in cross-section 

 and its cells are further differentiated than those in the more anterior region, 

 Pb, periblastic material and large nuclei between the embryo and the yolk. 



39 



