VUl PREFACE 



number of biologists have been skeptical of the results ob- 

 tained in these investigations, and it also appears that many- 

 have been opposed to the fundamental conception that 

 mitochondria are bacteria. It was these circumstances 

 that urged the author to seek a rational hypothesis whereby 

 the significance of microorganisms in the cell could be ex- 

 plained. A study of the literature on "micro-symbiosis" 

 revealed a wealth of evidence that supports and emphasizes 

 the significance of bacteria in the origin of species. 



A principle that is so revolutionary as Symbionticism, 

 not only introduces a new principle in organic evolution, 

 but also inserts a new conception in heredity, development 

 and cell-structure. While it may not be "good scientific 

 form" to indulge in speculative hypotheses, the new view- 

 point affects the hypotheses and theories that are held at 

 the present time in major divisions of biology, and the 

 author has deemed it advisable to discuss some of these 

 problems. Obviously it would be most unusual if all the 

 hypotheses that are advanced in this book should in the end 

 prove to be correct. They are based upon some evidence 

 which in many instances is scanty, but in the present state 

 of knowledge it represents the only evidence available. It is 

 obvious that further and more extensive researches on the 

 particular problems may result in modifications and the 

 development of new hypotheses. These theories have been 

 included in this book mainly to indicate the feasibility of 

 Symbionticism, and to stimulate further researches on these 

 fundamental problems. 



It is pertinent to emphasize that the chief object of this 

 book is to summarize the evidence for the bacterial nature of 

 mitochondria, and to present some of the evidence that 

 demonstrates the fundamental role played by bacteria in 

 the origin of species. 



The search for evidence bearing on the theory has carried 

 me into many fields of biological science as well as into the 



