IDorf" The Phylogenetic and Ontogenetic Development 



of Individuality and Organismal Differentials 



Chapter I 



Transplantation and Individuality in Coelenterates 



and Planarians 



In the foregoing part we have discussed the organismal differentials 

 and their relations to organ and tissue differentials in the very complex, 

 phylogenetically higher organisms ; in a subsequent part we shall discuss 

 these differentials also in certain pathological growths, which develop in 

 vertebrates under abnormal conditions of stimulation. We now intend to 

 undertake the same analysis in normal invertebrates and lower vertebrates. 

 In each class of animals we wish to determine how far transplantation of 

 parts of organisms indicates the presence of organismal differentials and 

 what the relations of the organismal differentials are to the organ and tissue 

 differentials. 



In adult birds and mammals there is a very strong reaction against strange 

 individuality differentials, and against strange organismal differentials in 

 general ; the normal equilibrium is strictly autogenous ; it depends upon the 

 presence of the same individuality differential in all the important tissues 

 and organs, and it is disturbed and leads to notable reactions if small parts 

 of tissues possessing a strange individuality differential are introduced into 

 the animal body. The strong cellular reactions of the organism against inter- 

 ferences with its structural integrity indicate that this tissue equilibrium is 

 relatively fixed and rigid. The replacement of lost parts by the organism 

 is very much restricted and the reactions which take place, ultimately tend 

 to maintain or restore the characteristic structural pattern of the individual. 

 Associated with this fixity is the great complexity and differentiation in the 

 tissues of each individual, which does not allow fargoing adaptations to new 

 environmental conditions or a nevvformation of lost parts. The individual 

 represents, therefore, a rigid autogenous equilibrium between its constituent 

 parts. 



It was of interest to determine whether this association between the degree 

 of sensitiveness to and of reactivity against strange organismal differentials, 

 and the degree of structural fixity and rigidity of an organism extends through 

 the whole phylogenetic development. Such a parallelism would suggest that 

 a causal relation exists between these two sets of factors. 



The special conditions confronting investigations in these more primitive 

 organisms have made necessary in many cases different methods of experi- 

 mentation. Instead of transplanting small pieces of tissues or organs, a method 



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