226 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



particular to the changes in the head appendages which may be induced 

 in certain crustaceans and in which the activity of the nervous system is of 

 importance ; here, also, regeneration is on the whole limited to the extremities 

 and other appendages. 



In general, the transformation from one part of the body into another, or 

 from one organ into another, seems as a rule not to be a direct one, but this 

 change is apparently accomplished by the return of the part of the body or 

 of the organ involved to a more indifferent state, which subsequently assumes 

 the characteristics of the new part or organ. Furthermore, it appears that 

 with increasing phylogenetic development, cells with relatively great poten- 

 tialities of further differentiation may take over the newformation of organs. 



C. Transplantation and Individuality in Adult Amphibia 



In our discussion of organismal differentials in amphibia, we shall omit, 

 for the present, transplantations in which host and transplant, or host and 

 partner, are embryonal; these we shall consider later. Furthermore, some 

 transplantations in amphibia were used for the analysis of the factors under- 

 lying metamorphosis, and these investigations will also be considered sep- 

 arately. There remain for our present purpose a number of transplantations 

 in adult urodeles and anurans, two groups in which the results differ in 

 certain respects. Of special interest are the transplantations of pigmented to 

 white skin and vice versa, because the behavior of the pigment may serve 

 as an additional indicator of the reaction of the host against the graft. 



In the urodele, Triton alpestris, homoiotransplantation of skin succeeded 

 well, as did likewise heterotransplantation of skin from Triton alpestris to 

 Triton cristatus, but in the latter type the healing took place more slowly than 

 in homoiotransplants. The white transplant assumed gradually the dark color 

 of the host skin. On the other hand, Triton salaratus did not, as a rule, tolerate 

 transplants from Triton alpestris but casted them off (Taube). In the sala- 

 mander, Diemictylus viridescens, Collins and Adolph did not observe a differ- 

 ence between the results of autogenous and homoiogenous transplantation of 

 skin; both remained preserved, but in both, a re-organization of the pigmen- 

 tation took place. 



In anurans, the differences between the results of auto-, homoio- and 

 heterotransplantation of skin were more pronounced. We may here refer also 

 to transplantations in frog tadpoles, where autogenous transplants of white 

 skin to pigmented areas remained preserved, but very slowly, pigmentation 

 could occur in the graft, caused apparently by changes which took place in 

 the transplanted epidermis itself. After homoiotransplantation, the skin healed 

 in more slowly, a relatively rapid invasion of the white skin by the pigmented 

 cells of the host occurred, and lymphocytes accumulated underneath the 

 transplant (Cole). In adult Rana pipiens, according to Hadley, autogenous 

 surface epithelium and glands healed in well, whereas homoiotransplantation 

 of skin succeeded not as readily, the number of unsuccessful grafts being 

 greater and the pigmented cells of the host growing into the graft. Still less 

 favorable were heterotransplantations from Rana pipiens to Rana clamitans. 



