No. i.] 



REGENERATION OF TISSUE. 



As shown in Fig. 4, the tail of a tadpole, in which the major 

 component is R. palustris and the minor R. sylvatica, was cut 

 off obliquely, leaving a small amount of the dark ectoderm of 

 R. sylvatica on the upper side. The inner cells at the cut edge 

 all belonged to A', sylvatica. When the new tail developed, it 

 showed along its upper part the dark ectoderm of R. sylvatica, 

 that had developed from the small piece left at the time of the 



FIG. 4. 



operation. The area covered by the dark ectoderm was greater 

 than that left after the tail was cut off, but it cannot be stated 

 how much of this increase is due to the cells becoming flatter 

 and how much to new cells formed at the free edge. 



In another similar experiment, in which, however, the major 

 component was the dark species, R. sylvatica, and the minor 

 the paler species, R. palustris, the tail was cut off (April 27), as 

 shown in Fig. 5. A large area of light ectoderm was left on 

 the dorsal surface of the tail, and only a small amount of the 



FIG. 5. 



black ectoderm came to the edge of the lower part. On May 

 10, when the new tail was fairly well developed, it was found 

 to have its upper surface covered by light-colored ectoderm, 

 and its lower by dark ectoderm, while the interior mesodermal 

 pigment cells were like those of R. palustris. Each tissue had 

 regenerated its like, and the light ectoderm of the minor com- 

 ponent showed no influence of the other, dark ectoderm, even 

 along the line of contact where new cells were developing. 



