FURTHER EXPERIMENTS ON THE REGENERA- 

 TION OF TISSUE COMPOSED OF PARTS 

 OF TWO SPECIES. 



T. H. MORGAN. 



THE experiments that I made a year ago were undertaken 

 in order to find out if regenerated tissue, made up of cells 

 derived from two species, showed any mixing of the specific 

 characters of the two species. For this purpose I grafted the 

 tail of a tadpole of one species of frog upon the posterior end 

 of a tadpole of another species. Later the tail was cut off in 

 such a way (as indicated by the line b-b in Fig. 5) that the 

 ectoderm left at the exposed edge belonged in part to one 

 species, in part to the other. When the new tail regenerated 

 there was found to be no mixing of the characters of the ecto- 

 dermal cells along their line of contact in the new part. The 

 results were unsatisfactory 

 from one point of view, 

 inasmuch as the small 

 piece of ectoderm left after 

 the operation is carried out 

 to the tip of the new tail 

 and increases proportion- 

 ally less in area than the 

 rest of the new part, so 



FIG. i. 



that although it is highly 



probable that near the tip of the tail new ectodermal cells 

 are being formed by both kinds of ectoderm, still I did not 

 demonstrate that this is actually the case. Moreover, I found 

 that in the later stages the difference in color between the 

 two kinds of ectoderm was less marked than at first, so that 

 the experiment would have been more convincing had the tail 

 been cut off at an earlier stage. This I have done during 

 the present spring, and the results in regard to the ectoderm 



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