Fig. 35. The formation of a secondary head after transplantation of regions 

 1 and 2 in the early gastrula. Top: Regions 1 and 2 are transplanted into 

 another gastrula in such a way as to bring them into contact with the presump- 

 tive epidermis. The second gastrula forms a primary neural plate and a secondary 

 neural plate. The final result (bo/low) is an embryo with two heads. It is 

 important to note that the secondary embryo contains only a very small amount 

 of tissue contributed by the transplant. Most of the tissue comes from the host. 



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