Schneider : the phenomena of SYMBIOSIS. 931 



III. Mutualistic Symbiosis. 



1. Nutricism (Semi- mutualistic Symbiosis). 



2. Mutualism. 



3. Individualism. 



a. Semi-individualism. 



b. Complete Individualism. 



IV. Compound S}''mbiosis. 



These phenomena are represented by the association of 

 widely different organisms. Organisms similar to those which 

 enter into'an antagonistic symbiosis will occur in mutualistic 

 symbiosis. This seems to indicate that the development of 

 these associations depends largely upon opportunity (environ- 

 ment). To some extent, however, the organisms control or 

 modify the symbiotic relationship as indicated in the introduc- 

 tion. A classification of the phenomena indicating their phylo- 

 genetic relationship can therefore not be based upon the organ- 

 isms which enter into their formation. One can only indicate 

 the physiological relationship of the phenomena and their ap- 

 proximate relative evolution. 



The accompanying figure and the brief discussions of the 

 phenomena will doubtless suffice to make clear their relation- 

 ships and limitations. The figure is intended to indicate the 

 phylogenetic relationship of the symbioses without any refer- 

 ence to the phylogeny of the organisms comprising them. Ac- 

 cidental symbiosis is indicated as forming the basis from which 

 the other forms developed. Parasitism should, perhaps, have 

 been indicated as taking its origin below nutricism. Saprophy- 

 tism proper is not symbiosis. It is introduced in the figure to 

 show its probable relationship to the symbiosis. The only 

 compound symbiosis indicated is that of mutualism with para- 

 sitism. Further investigations may reveal others. 



