14 MORGAN. 



In addition to these experiments I have records of four others 

 similar to Experiment I (Fig. 2, A, B) ; three others similar to 

 Experiment II (Fig. 3); and four others in which the tail was 

 cut off obliquely, leaving both kinds of ectoderm at the cut 

 edge. In all cases the specific character of the new tissue was 

 like that of the old tissue from which it arose. 



At first the difference in the ectoderm of the two species is 

 very marked, but as the tadpoles get older the ectoderm seems 

 to flatten and become more transparent, so that in these tad- 

 poles it is difficult to distinguish between the two kinds of 

 ectoderm. But if the tadpoles are examined every day one can 

 detect differences in the two kinds of ectoderm for a longer period 

 than could be done by casual observations alone. Wherever 

 the ectoderm has not spread out, particularly at the tip of the 

 tail, the dark pigmented cells of R. sylvatica and the yellowish 

 cells of R. palnstris can be readily detected. The pigment 

 cells in the mesoderm assume their characteristic arrangement 

 during the older stages, and as the ectoderm becomes more 

 transparent, the cells can be easily seen in the living tadpoles. 

 The tadpoles were all kept under the same condition, so that 

 the effect of light on the pigment cells would be approximately 

 the same in all experiments. 



Unfortunately the differences in pigmentation are the only 

 specific characters that can be made out readily in these tad- 

 poles, but I think there can be little doubt that if the cells 

 retain their characteristic pigmentation they also retain their 

 other peculiarities. 



We may conclude with some degree of probability that during 

 regeneration in a region where the cells have been derived from 

 two different species, each kind of new cell retains the char- 

 acter of the cells from which it is derived, and the specific 

 characters of the cells of one species are not transmitted to the 

 cells of the other species, although the developing cells in the 

 new tissue may be in actual contact. 



