No. 3-] THE REGENERATION OF TISSUE. 117 



and Fig. 2,a-a, but unfortunately the two lots were not kept sepa- 

 rately. On April 29 when again examined new tails had begun 

 to regenerate, and two individuals out of the nine showed that 

 the core of the new tail was compound in character. In both 

 the major component was black and the minor yellow. In one 

 of these the new tail was yellow on the dorsal side and black 

 on the ventral, and in the other the new tail was black on the 

 dorsal side and yellow on the ventral. 



In another series the experiment was somewhat different. 

 The grafting took place on April 17. Two days later the ecto- 

 derm of the minor component had been carried out further on 

 the tail (Fig. 5), so that at the base of the tail the inner tis- 

 sues of the minor component were covered by the ectoderm of 



FIG. 5. 



the major component. At this time (April 19) the tail was 

 cut off obliquely, as indicated by the line a-a in Fig. 4, leaving 

 the inner tissues of both components exposed at the cut sur- 

 face. On May 19 all three of the tadpoles that had been 

 operated upon showed a compound tail. One of these tadpoles 

 was R. palustris and the other two were R. sylvatica, with 

 grafted tails of the other species, respectively. 



In a third series of five individuals, grafted April 19 and cut 

 off April 20, as in Fig. i, two showed later a compound tail; 

 and in a third I was in doubt whether or not a few of the 

 yellow cells of the major component entered the new tail. 



In three later experiments in which the tail had been cut 

 off, so that a smaller piece of the minor component was left 

 attached, a larger number regenerated compound tails. 



In one of these experiments the grafting took place on 

 April 27, and the tail was cut off on the following day. One 

 of the three produced a tail composed of both kinds of tissue. 



