252 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



the surrounding host tissues did not show a marked activity. However, in 

 the majority of cases the implanted material, it seems, was absorbed without 

 having led to the formation of these embryomata. 



In such transplantations, certain substances in the host may be toxic for 

 the transplant, and, conversely, there is a tendency also for the hosts to be 

 injured by the transplants and they may die within a few months. The toxic 

 substances in the peritoneal cavity were found by A. Weber to be identical 

 with substances present in the blood or lymph. Especially the eggs of Triton 

 appear to be killed within a few minutes by such substances in an adult 

 Triton. On the other hand, eggs of Bufo and Bombinator develop in the 

 peritoneal cavity, or in the lymph sacs of adult animals of their own species, 

 without being injured by toxins. But if Triton eggs, which would have died 

 within five minutes in the peritoneal cavity of adult Tritons, are transplanted 

 into the lymph sac of Bufo, they develop, although abnormally. Anuran 

 eggs live for several hours in the peritoneal cavity of Triton. It seems, then, 

 that it is particularly the eggs of Triton which are sensitive to these toxic 

 substances. 



It is not sufficiently clear in these experiments what role organismal differ- 

 entials may play in producing such toxic effects. However, according to Weber 

 the eggs survive longer in the peritoneal cavity of the parents than in 

 homoiogenous individuals. While this indicates that organismal differentials 

 may in some way be concerned in these processes, it is probable that 

 essentially we have in these experiments to deal with the presence of special 

 toxins, distinct from the heterodifferentials, which affect injuriously the 

 transplants after ordinary transplantations. 



Transplantation of avian embryonal tissues into adult birds. In the ma- 

 jority of experiments avian embryonal tissues were homoiotransplanted into 

 the subcutaneous tissue, muscle of the chest, peritoneal cavity, or anterior 

 chamber of the eye of adult birds (Fere, Wilms, Tiesenhausen and Skubis- 

 rewski). One-day-old embryos were not found suitable for transplantation; 

 experiments with young embryos, about five days old, appeared most suc- 

 cessful. The gross observation indicated that in the majority of cases the 

 transplants did not grow, or growth disappeared within a month or two. In 

 some instances, however, masses of irregularly arranged embryonal tissues, 

 embryomata, developed, which grew to larger size and remained alive for a 

 year or more; but in the end they also diminished again in size and were 

 absorbed. Certain tissues, such as bone, cartilage, smooth muscle and 

 squamous epithelium, were especially resistant. There was apparently no 

 difference between the results, irrespective of whether the embryonal material 

 was transplanted into the mother or into non-related individuals of the same 

 species. However, considering the great variability in the results obtained in 

 these experiments, definite conclusions cannot be drawn as to the effects 

 of the relationship between transplant and host, although it seems that hetero- 

 transplantations, such as those of chick embryo to duck or pigeon, of duck 

 embryo to chicken or pigeon, or also of mammalian embryo to chicken, resulted 

 in an early degeneration of the transplants. 



