HIGHER INVERTEBRATES AND AMPHIBIA 229 



An internal secretion is also active after homoiotransplantation of thumb- 

 pads of the frog; however, in this case the testicular hormone affects only the 

 further growth processes in the organ after it has healed in; and according 

 to Harms, it accomplishes this effect largely by means other than variations 

 in the circulatory condition and blood supply received by the transplant. 



Rhoda Erdmann noted that in the adult Rana autotransplantation of skin 

 succeeded well; but homoiotransplantation succeeded only for periods of 

 from two to four months, and skin glands did not develop in the latter kind 

 of transplants. But even after heterotransplantation from Rana temporaria 

 to Rana arvalis the graft could remain attached to the host for as long as 

 eighty days, when it was cast off. Similar to the observations of Harms as to 

 toxic effects exerted by ovaries transplanted into Triton, and to those of 

 Diirken in the transplantation of parts of neurulae into larvae of Rana, Erd- 

 mann noted after transplantation of skin of Hyla to Rana, the occurrence of 

 hemorrhages and other toxic symptoms in the host. These results agree also 

 with those of Schultz, who found that after transplantation of skin from Bufo 

 viridis to Bufo vulgaris, the host died, while the reciprocal transplantations 

 were successful. It is evident that specific toxins given off by such transplants 

 complicate the results of grafting in these amphibia, and that we have not 

 merely to deal with the effects of organismal differentials. As stated above, 

 similar effects have also been observed after transplantation in certain 

 urodeles. 



We may then conclude that heterotransplantations succeed with greater 

 difficulty in urodeles than in lower classes of animals, and with still greater 

 difficulty in anurans. In the latter class some differences have been recorded 

 even between the results of homoio- and autotransplantation, and we may then 

 conclude that a furthergoing stage in specialization of these differentials has 

 been reached in amphibia, and that within the amphibia there is seen a graded 

 advance in the refinement of the organismal differentials in the transition from 

 urodeles to anurans. However, as we pointed out previously, the lack of an 

 unfavorable reaction of a host against a certain kind of transplant does not 

 exclude the presence of the finer grades of organismal differentials. Thus we 

 cannot exclude the possibility that in urodeles, as well, individuality differen- 

 tials may exist; indeed, certain observations indicate that here, also, auto- 

 transplantation may succeed better than homoiotransplantation. 



The interpretation of the results of transplantations in the more primitive 

 organisms which we have discussed so far, is based largely on the gross 

 examination of the transplants ; however, in the case of grafting in the urodele 

 Triturus, Anderson and Horowitz have carried out microscopical examina- 

 tions, in which they compared the reactions in auto-, homoio-, and hetero- 

 transplantations of skin (Anderson), and muscle tissue (Horowitz). Horo- 

 witz has described a reaction of the fibroblasts and lymphocytes of the host, 

 which invaded the transplant the more actively, the stranger the organismal 

 differentials were between host and transplant. In the case of heterotrans- 

 plants, also polymorphonuclear leucocytes participated in this reaction. These 

 various cells succeeded in destroying tissues possessing organismal differ- 



