206 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



latter extend their sphere of influence to distant parts, perhaps through diffu- 

 sion of contact substances into distant areas of the body. Thus a well dif- 

 ferentiated organ may be able to force a distant part of a transplant to form 

 a heteromorphic organ, counter to its normal rudimentary differentiation. 

 In this case, the size of the transplant becomes one of the determining factors. 

 If the transplant exceeds a certain size, then its rudimentary preformed 

 differentiation is able to control the regenerative, heteromorphic tendency of 

 the host organ. Such a predifferentiation in the transplant may determine the 

 mode in which the whole organism shall be formed, its integrative action 

 inducing the formation of oral and aboral organs in accordance with the 

 structure of the transplant, which may thus dominate over the integrative 

 tendencies in the host. If a small piece is transplanted, there is evidently not 

 enough material present to allow its predifferentiation to assert itself, because 

 its opposite poles are very near to each other; the host, which is the larger 

 partner, then dominates and apparently induces degenerative processes in 

 the transplant, leading to its absorption. Perhaps the amount of active sub- 

 stance produced by short pieces is too small to overcome the opposing tend- 

 encies inherent in a larger piece. 



A lack of a sufficient degree of predifferentiation in the transplant may 

 be the reason why, under certain conditions, it cannot maintain itself in 

 competition with the host and, instead, is absorbed by the latter. This applies 

 especially to pieces from the middle zone; and, correspondingly, the middle 

 zone of the host, by not inducing differentiation in a transplant, may lead to 

 its absorption. On the other hand, if, as a result of the combined organizer 

 and regenerative action, a part of an organism has been duplicated, the 

 restitutive tendency can lead to a separation of the duplications, which may 

 be followed by the formation of two independent organisms. 



The tendency to supplement by regeneration a part of an organism in such 

 a way that a whole predifferentiated organism develops has a counterpart in 

 the tendency to form a normal whole from an organism, in which, through 

 transplantation, a surplus of certain organs, for instance, tentacles, has been 

 produced. The disequilibrium thus induced leads either to certain degenerative 

 processes, presumably agglutination and reduction, or it may act as a stimulus 

 to the production of certain organs, an effect which indirectly brings about the 

 loss of excessive parts. The predifferentiated organism represents an equili- 

 brated system, and disturbances in this system initiate various reactions aiming 

 at the restitution of its equilibrium. It is remarkable how varied and different 

 the mechanisms are which in the end all lead to the same result, the integrative 

 newformation of an equilibrated whole. 



In the experiments on which these conclusions are based transplants influ- 

 enced the host and induced in it the newformation of organs, thus acting as 

 organizers, or in other cases the transplants influenced the restitutive, regen- 

 erative activities of the host by actions at a distance; conversely, the host in- 

 fluenced, under certain conditions, also the regenerative or restitutive activity 

 of the transplant. In these instances, as stated, certain organs, usually the 

 more differentiated ones, are dominant over others and force those parts of 



