CHEMICAL COMPOUND 

 IN EGG ALBUMEN 



NORMAL NEURAL TUBE 



IMPLANT 



INDUCED NEURAL TUBE 



Fig. 39. Chemical compounds induce neural tubes. The chemicals are dis- 

 persed in egg albumen and the mixture is placed in the blastocoel of an early 

 gastrula. At the end of gastrulation the implanted mixture is found in contact 

 with the ventral epidermis. Later a cross section of an embryo reveals an induced 

 neural tube. 



