THE "organization CENTRe" 65 



having been grafted into the cristalus skin region, 

 developed into skin (Fig. i6). Both the pieces of tissue, 



Fig. 16. — Spqmann's exchange experiment (from Diirken, after 

 Spemann). {a) A gastrula of Triton alpestris with a small dark 

 implant of the presumptive neural tissue from Triton taeniatus. 

 {b) The alpestris embryo at a later stage with the taeniatus tissue 

 forming part of its skin 



in fact, developed in accordance with the region 

 into which they were grafted, and not in accordance 

 with the region from which they originally came. 



