HIGHER INVERTEBRATES AND AMPHIBIA 223 



We may conclude from the principal facts relating to organ and organ- 

 ismal differentials in the relatively primitive classes which we have considered 

 so far, that while with the progress in phylogenetic development the differen- 

 tiation of the organs advances, their plasticity decreases and, correspondingly, 

 the effectiveness of the inductive processes leading to the reestablishment of 

 normal individuals is diminished ; however, there is not a proportional advance 

 noticeable in the differentiation of the organismal differentials, or at least in 

 their manifestation. In all these classes heterotransplantation between nearly 

 related species seems to succeed, although as a rule with greater difficulty than 

 between homoiogenous organisms, while between farther distant species it 

 does not succeed. But, it is possible that the greater regenerative power of the 

 hydroids and also of the planarians, as compared with that possessed by 

 lumbricidae, — a regenerative power which leads to integration of defective 

 organisms, — may serve to cover up the fact that they actually do possess less 

 differentiation of the organismal differentials than the lumbricidae and less 

 sensitiveness to strange differentials. The greater regenerative power of the 

 hydroids may lead to a more ready outgrowth from a cut surface and to 

 subsequent separation of the partners in case the organismal differentials 

 are not quite compatible, and this condition may make it appear as though the 

 reactions against differences in organismal differentials were more severe in 

 the more primitive organisms than they actually are. 



B. Transplantation and Individuality in Arthropods and Echinoderms 



In general, the regenerative power is very limited in insects and moths, 

 especially after metamorphosis has taken place, and this condition interferes 

 with transplantability to a certain extent. It also seems to be associated with 

 an increase in the rigidity of organization. 



In moths, experiments in transplantation were carried out by Crampton 

 as early as 1899. At that time, as we stated in reference to experiments in 

 lumbricidae, the problems of polarity and of the preservation of the species 

 characters in transplant and host were prominent; also, the question as to 

 the behavior of the various organs of host and transplant to each other had 

 been introduced through the experiments of Born with embryos of amphibia. 

 On the other hand, the problem as to the effects of variations in relationship 

 between the partners, or between donor and host, on transplantation played 

 an unimportant role at that time. In Crampton's experiments parts of pupae 

 were used ; on account of their low regenerative power only the skins or other 

 organs situated near the surface, but not the internal organs, united after 

 transplantation, and positive results were obtained therefore only in a minority 

 of cases. While homoiotransplantation of small pieces of tissue was successful 

 in a number of instances, heterotransplantation succeeded not at all, or at 

 best only exceptionally. However, if instead of grafting small pieces of tissue, 

 whole segments of the animals were transplanted, a procedure which does 

 not exactly correspond to parabiosis because of the inability of the isolated 

 segments to lead an independent existence, both homoio- and heterotrans- 

 plantation succeeded, but the former apparently somewhat better than the 



