PRESUMPTIVE EPIDERMIS 



PRIMITIVE STREAK 



DUCK 



CHICK 

 NEURAL TUBE 



DUCK 

 NOTOCHORD 



CHICK 

 NEURAL TUBE 



CHICK 

 NOTOCHORD 



Fig. 38. The organizer in the blastoderm of birds. Upper figure shows duck 

 blastoderm. The anterior end of the primitive streak is cut out and transplanted 

 into the presumptive epidermis of the chick blastoderm. Lower figure shows two 

 neural tubes of chick ectoderm, one induced by chick notochord, the other in- 

 duced by the transplanted duck notochord. 



81 



