SYMBIONTICISM 63 



parently, grow only in the presence of certain other 

 bacteria. One organism produces extrinsic conditions 

 that are essential for the hfe of another. Their relation- 

 ship is more in the nature of an indispensable association 

 and has nothing to do with prototaxis. It is possible that 

 bacteria may also play the role of relative or host sym- 

 biont. The D'Herelle phenomenon would allow of such 

 a possibihty. 



Mitochondria represent one of the sjTnbionts in the 

 expression of a positive prototaxis resulting in an absolute 

 symbiosis. The universal presence of mitochondria in 

 the cells of all plants and animals constitutes evidence 

 that the development of such relationships is not a digres- 

 sion from normal biological behavior, but rather the result 

 of a fundamental principle. The universahty of positive 

 prototaxis resulting in absolute symbiosis, or Symbionti- 

 cism, forces us to recognize this as of fundamental impor- 

 tance. Just as reproduction insures the perpetuation of 

 existing species, the author beheves that Symbionticism 

 insures the origin of new species. 



In absolute symbiosis, the adjustment responses of the 

 two symbionts have been completed, making it difficult 

 to recognize their exact nature. On the part of the bac- 

 terial symbiont, it appears, however, that one response 

 has been the development of fragihty. While it is quite 

 impossible in most cases to recognize the complete modifi- 

 cations that have occurred in the host cell in absolute 

 symbiosis, modifications are specifically indicated in many 

 of those that are as yet incomplete. 



It is recognized that the ideas on symbiosis embodied in 

 this book are at variance with those usually conveyed by 

 this term. It is perhaps unfortunate to utilize an estab- 

 Ushed terminology with a new meaning as it may lead to 

 confusion. Nevertheless, the author believes that in this 



