REGENERATION OF TISSUE COMPOSED OF 

 PARTS OF TWO SPECIES. 



T. II. MORGAN. 



BORN'S experiments in grafting together tadpoles of different 

 species of frogs have demonstrated that each part, whether 

 large or small, retains the characteristics of the species to which 

 it belongs. During the development of an animal, formed by 

 the union of parts of two species, the tissues do not influence 

 each other, but each develops its own specific peculiarities. 



Joest has shown that when parts of two different species of 

 earthworms are grafted together each part retains its specific 

 characters. He has further shown that if, after grafting, a 

 portion of one of the parts is cut off, the new part that is 

 regenerated is like the part from which it immediately arises, 

 and is not influenced by the part belonging to the other spe- 

 cies, even when the latter is very large, and the former (that 

 from which the new part arises) is very small. 



Many experiments have been made with plants in which 

 different species have been grafted together, and the subsequent 

 growth of the two parts studied. Vochting, who has given a 

 detailed account of these experiments and has made others 

 himself, has shown that in general no influence of a specific 

 character is transmitted from one part to the other, although 

 in certain cases 1 the parts do have some influence on each 

 other. 



The following experiments were made, not so much to deter- 

 mine whether the tissues of one component of a graft influence 

 the kind of regeneration of the other, since this point seemed 

 fairly settled by Joest and by Harrison, but I hoped to find out 

 if new tissue, made up of cells derived from parts of two species, 

 showed any mixing of the specific characters of the two species. 



1 Particularly in those cases where annual and biennial varieties are grafted 

 together. 



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