ORGAN DEVELOPMENT IN VERTEBRATES 



275 



(Fig. 12.12). This gradient is probably not a straightforward reflection 

 of the intrinsic capacities of the flank mesenchyme, but is partially a result 



so 



¥0 



20 



10 



Figure 12.12 



Limb induction in the newt. The graph above shows the frequency with 

 which hmbs (thick line) or pelvic girdles (thin line) were induced by the 

 implantation of nasal placodes in the corresponding region of the flank 

 indicated on the drawing below. In the drawing the position of the normal 

 limbs is shaded, that of the pronephros dotted. (From Balinsky 1933.) 



of the general influence of the body as a w^hole. Thus Takaya has shov^n 

 that if material from the lowest point in the gradient (just in front of the 

 hindlimb-bud) is transplanted to a more anterior position, and then sub- 

 mitted to the influence of an implanted inductor, the frequency of limb 



