INTRODUCTION 7 



fundamentally different from inorganic evolution. Inor- 

 ganic chemical reactions are dependent on the same set of 

 extrinsic factors that govern organic chemical reactions. It 

 appears, also, that the fundamental principle involved in the 

 origin of species is primarily of the same general nature as 

 it is in the origin of chemical compounds. Thus, just as it is 

 necessary for two or more chemical compounds to be brought 

 together if a new compound is to be formed, it may be 

 necessary for two or more forms of life to unite in the pro- 

 duction of a new species. 



While we lack specific data on some phases of plant and 

 animal behavior, it appears from general observations, that 

 higher plants and animals exhibit a greater degree of sta- 

 bihty than do the lower forms. The lowhest forms of 

 Ufe — the bacteria — appear to exhibit the greatest degree 

 of variabiUty. These lowly forms which, apparently, 

 are neither plant nor animal, appear to respond more readily 

 to environment than do the complex forms of hfe. It has 

 been suggested, and it appears hkely, that the bacteria are 

 the primordial organisms from which all higher organisms, 

 both plant and animal, have sprung. 



The nature of the process by which this phase of organic 

 evolution may have occurred is indicated in the phenomenon 

 symbiosis. Notwithstanding the fact that symbiotic rela- 

 tionships have been studied for many years, the fundamental 

 principle embodied in the phenomenon does not appear to 

 have been recognized. This, probably, is due to the fact 

 that the first recognized examples of symbiosis dealt with 

 those cases in which both symbionts were complex animals 

 or plants, and the life relationship was looked upon more in 

 the nature of a biological curiosity, than the expression of a 

 fundamental principle. A more universal type of symbiosis 

 is represented in those relationships in which one symbiont 

 consists of a microorganism. It is this latter type which 

 may be designated '^microsymbiosis" that appears to offer 

 the solution to the problem of the origin of species. 



