242 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



must therefore consider the possibility that specific toxic substances distinct 

 from the organismal differentials were responsible for some of the results fol- 

 lowing heterogenous, and even homoiogenous combinations. 



When we review this entire series we come to the conclusion that there is 

 no very definite gradation noticeable in the joining together of different in- 

 dividuals, if we ascend from the ontogenetically lower to the more adult 

 forms. However, there develops in every case an incompatibility between 

 farther distant heterogenous parts of an artificial combination, and it is often 

 noticeable also between more nearly related heterogenous partners; on the 

 other hand, there is usually no definite incompatibility between homoiogenous 

 partners, although even here some abnormalities may be found. 



However, there are several difficulties in interpreting these findings. In the 

 first place, as stated above, these investigations were not carried out with a 

 view of analyzing the organismal differentials and therefore the experimental 

 data which would make possible such an analysis are very incomplete. Sys- 

 tematic comparisons between auto-, syngenesio- and homoiotransplantations 

 were in no case made. Secondly, it is possible that in some instances factors 

 of secondary importance came into play, such as the more or less accidental 

 differences in the size of the surfaces which were to be joined together. 

 Thirdly, there are some indications that organ differentiations and the inter- 

 actions of organs that adjoined each other played a definite role in determin- 

 ing compatibility; this is suggested by the importance of the orientation of 

 the surfaces of contact. In addition, there may have been active, specific 

 toxic actions, which were referable not to the whole organism as such and to 

 its organismal differentials, but to specific metabolic processes of certain 

 organs, and which were comparable to the toxins produced in the glands of 

 some amphibia and reptiles. 



Notwithstanding these difficulties of interpretation, there is very little doubt 

 that essentially the results of the joining together of two ontogenetically 

 primitive organisms depend upon the compatibility of their protoplasms, and 

 in particular, of their ectoplasmic layers, which presumably form around 

 wound surfaces of cells. But, while a coalescence takes place only between 

 homoiogenous individuals, or possibly between individuals belonging to very 

 nearly related species, the primary agglutination process seems to be less 

 specific, although specificity is not lost entirely. Furthermore, we find here, 

 opposed to the tendency to coalesce and to form one unified organism, a 

 tendency towards regeneration and the development of two distinct organ- 

 isms similar to that which we observed in transplantations among phylo- 

 genetically primitive organisms. This applies especially to heterotransplanta- 

 tions. The more suited to each other the character of both the protoplasms 

 and the surfaces of contact, the less this regenerative tendency will assert 

 itself. Instead, integrative mechanisms, which tend to make one single organ- 

 ism out of the two, dominate. While it is impossible to form a definite 

 concept as to the relative importance of physical and chemical factors which 

 may assert themselves at the place of union, still it is evident that the degree 

 of relationship between two embryonal organisms is one of the factors 



