HIGHER INVERTEBRATES AND AMPHIBIA 227 



The healing-in took place with greater difficulty and pigmented grafts that 

 remained attached to the host for more than 15 days became progressively 

 lighter, whereas the unpigmented grafts were invaded by the pigmented host 

 skin; degenerative changes took place in the transplant and large masses of 

 leucocytes collected underneath it. There were then, in anurans, graded 

 differences in the tolerance of the host to autogenous, homoiogenous and 

 heterogenous transplants, and the reactions against strange organismal dif- 

 ferentials were, here, more definite than in urodeles. It is of interest that 

 heterotransplantation into the lymph-sac succeeded, and this suggests that it 

 was the action of the tissues rather than that of the bodyfluids which caused 

 the injury of the heterogenous graft. 



We may mention in this connection also similar experiments of May in 

 reptiles. In chameleon, May found that autotransplantation of skin succeeded 

 very readily, without any change in the pigmentation of the transplants. On 

 the other hand, homoiotransplants were absorbed after they had healed in, 

 the total absorption taking place between the 61st and 90th day. Usually no 

 change in pigmentation occurred here, except in one case, where the trans- 

 plant became lighter. Conditions were then, in this case, similar to those seen 

 in birds and mammals, except that the reactions occurred more slowly; 

 whether or not lymphocytes participated' in these experiments in reptiles is 

 not stated. 



The results of transplantations of other organs are in essential agreement 

 with those we have mentioned. Thus, in the salamander, Diemictylus viri- 

 descens, Stockard found that homoiotransplanted pieces of the ovary can be 

 maintained alive in a satisfactory condition in the testicle, but not in other 

 organs. However, in other urodeles, Harms showed that not only homoio- 

 transplantation, but even heterotransplantation, of the ovaries may succeed 

 within a certain range of relationship, and that in general there seems to be a 

 parallelism in the transplantability of tissues and the possibility of hybridiza- 

 tion between certain species. In this connection, Harms made the interesting 

 observation that in urodeles blood vessels of heterogenous origin supply the 

 circulation in these transplants, and that the peritoneal cells lining the grafted 

 ovaries may swell, send out processes in the direction towards the lining 

 peritoneal cells of the host, and that both may then meet and coalesce. In adult 

 urodeles, therefore, heterogenous cells may enter into close contact with each 

 other, or may coalesce apparently without the development of any antagonistic 

 reaction. Meyns noted a similar coalescence of cells also in anurans, but it 

 occurred in homoiogenous transplantations. In case a destruction of the 

 heterotransplanted ovary did take place, this may not have been altogether a 

 direct effect of heterotoxins, inasmuch as connective tissue and phagocytic 

 cells of the host took part in the disintegration and elimination of those trans- 

 planted ova which had escaped the direct toxic action of the bodyfluids of the 

 host. It seems, therefore, that ova which, under the influence of the strange 

 organismal differential were changed in their metabolism, secondarily were 

 exposed to the injurious action of host cells. 



In mammals we observed in certain cases that reciprocal transplantations 



