No. 3-] 



THE REGENERATION OF TISSUE. 



119 



In several cases double tails grew out enclosed in the same 

 common fin, and lay usually in the same plane. In some cases 

 the core of one of the new tails was derived from one of the 

 components and the other from the other component. In 

 several cases one or the other new tail received material from 

 both components. In one of these cases it could be seen with the 

 greatest clearness that the compound tail received material from 

 both sources (Fig. 7). 

 Cases of this kind are 

 particularly convincing, 

 since they furnish all 

 the data for comparison 

 between the two kinds 

 of regenerating tissue 

 of the two components. 

 The dorsal tail was 

 yellow and the upper 

 part of the ventral tail 

 was also yellow, and its 

 tissue precisely like that of the dorsal tail. The pigment cells 

 also of the yellow component extended out on to both tails. 



These cases of double tails are probably due to imperfect 

 grafting, - -the notochorcl and nerve cord of the two compo- 

 nents not being in the same position, so that when the tail is 

 cut off both sets of structures are exposed and a tail develops 

 from each. 



Conclusions.- -The experiments demonstrate that a single 

 tail may be formed by the regeneration of tissue derived from 

 two species, and that in such cases there is no specific change 

 produced in the one kind of new tissue by the other. Each 

 kind of tissue regenerates its like, and the two kinds combine 

 to form a single morphological organ, --the tail. 



FIG. 7. 



May, 1900. 



