300 



Experimental Zoology 



similar kind gave the same result. Especially instructive is 

 the case where the nev^ ectoderm is derived partly from one 

 component, 'partly from the other species (as when the tail is 

 cut off as shown at h-h in Fig. C). No influence of the ecto- 



FiG. 22. Grafted tail of frog. Fig. A, Rana sylvatica with grafted tail of 

 Rana palustris. Fig. B, reciprocal graft. Fig. C, late stage of last. Fig. D, 

 newly regenerated tail of Fig. A cut off at a-a. Fig. E, newly regenerated tail of 

 Fig. C cut off at a-a. 



derm cells on each other could be detected, although they are 

 in intimate contact. 



The attempt to unite pieces of brown hydra, H. fusca, to 

 pieces of green hydra, H. viridis, has not succeeded. Wetzel 

 has shown that although the two pieces will stick together for 

 a few hours, or even days, they subsequently separate ; but the 

 union of Hydra fusca and H. grisca v/as successfully carried out. 



