144 PHARMACEUTICAL BACTERIOLOGY 



These phenomena are represented by the association of widely, differ- 

 ent organisms. Organisms similar to those which enter into an antago- 

 nistic symbiosis may also occur in mutualistic symbiosis. This seems 

 to indicate that the development of these associations depends largely 

 upon opportunity (environment). To some extent, however, the organ- 

 isms control or modify the symbiotic relationship. A classification of 

 the phenomena indicating their phylogenetic relationship can therefore 

 not be based upon the phylogenesis of the organisms which enter into 

 heir formation. One can only indicate the physiological relationship 

 of the phenomena and their approximate relative evolution. 



i Incipient Symbiosis (Indifferent Symbiosis) 



Under incipient symbiosis are included the multitudinous phenomena of 

 symbiotic relationships, which have not yet acquired evident antagonistic 

 or mutualistic characters. In many instances there are marked morpho- 

 logical adaptations, but without any apparent corresponding functional 

 modification. In far the greater number of cases there is simple contact, 

 resulting from over production. In view of this fact one may be criticised 

 for recognizing such relationships as symbioses. From a priori reasoning 

 one is, however, forced to conclude that the first symbiotic activities began 

 with the first contact of organisms. Incipient symbiosis, therefore, forms 

 the basis or common source of all symbiotic phenomena. From it gradu- 

 ally emerged highly complicated morphological and physiological adapta- 

 tions of originally independent (self-sustaining) organisms. There is also 

 little doubt that as our methods of investigation become more highly 

 perfected, many of the symbiotic phenomena now considered as indifferent 

 will be relegated to the realms of antagonistic or mutualistic symbiosis. 



i. Accidental Symbiosis. This represents the least specialized form of 

 symbiosis, but is of wider occurrence than all the others combined. Acci- 

 dental symbiosis is represented by the mere coming in contact of two or 

 more morphologically distinct organisms; such contact being, however, 

 sufficiently prolonged to give it the semblance of a symbiosis. Mere 

 momentary contact is not symbiosis as here understood. 



Accidental symbioses are particularly numerous where there is luxuri- 

 ant growth, hence where competition is great, as in the tropics and in 

 highly productive soils generally. The lower parts of plants in green-houses 

 are covered with bacteria, hyphal fungi, algae and more rarely some of the 

 lower protozoa. The epidermal cells of many plants contain more or less 

 bacteria. Submerged plants are covered with mollusks, hydras, tubulari- 

 ians, amebas, vorticellas, etc. The larger land and water organisms 

 furnish hiding places and protection for hosts of smaller organisms. 



