140 PHARMACEUTICAL BACTERIOLOGY 



continued (perhaps more or less interruptedly), the morpho-physiological 

 changes progressed in the direction of parasitism and away from inde- 

 pendence. Finally the originally independent chlorophyll-bearing and 

 carbon assimilating organism became wholly dependent upon an organic 

 food supply and sustained a total loss of the chlorophyllian function. 

 There is no doubt that the host plant or host plants are also more or less 

 affected by the symbiosis. The relative morpho-physiological changes 

 are approximately in proportion to the size (volume) and biological ac- 

 tivity of the associating organisms. 



It is necessary to keep distinct the difference between mere associations 

 and societies of organisms, and symbioses proper. There is scarcely a 

 problem of economic significance which is not directly associated with 

 some form of symbiotic relationship of organisms. One needs but call 

 to mind the recent discoveries in the treatment of disease, modern surgery, 

 agriculture, dairy industries, etc. A mere mention of all the experimenta- 

 tions and discoveries in connection with symbiosis would fill volumes. 

 Much careful research is yet necessary in order to clear up the uncertain- 

 ties in regard to the biological significance of many of the symbioses. In 

 order to impress this uncertainty more fully we shall mention a few symbi- 

 otic phenomena which are either not recognized as such, or improperly 

 classified, usually as parasitism. 



Unclassified Symbiotic Phenomena. Under this heading will be 

 briefly mentioned numerous and varied phenomena which are of undoubted 

 symbiotic nature, but are not as yet clearly understood. Some of these 

 phenomena are of a very complicated nature and indicate a long phylo- 

 genetic development. In many instances the morphological adaptation 

 and relationship of the organisms is so remote as to awaken serious doubt 

 as to its symbiotic nature. Under this category belong the mutual 

 adaptation of plants (entomophilous and other flowers) and insects; also 

 the various forms of mimicry; the association of various species of aphidae 

 and ants upon certain plants; besides many other phenomena. The associa- 

 tion of trees, such as the myrmocophilous Cecropias and representatives of 

 other genera, with ants, is by many designated as true mutualistic symbiosis. 



The relation of the male and female reproductive cells is of a truly 

 symbiotic nature. It represents a highly specialized form of individual- 

 ism. The relationship existing between the immature embryo and the 

 food-supplying parent-stock is evidently a form of symbiosis. There are 

 numerous instances in both the animal and vegetable kingdom in which 

 the more or less imperfect but complete second generation lives in a sym- 

 biotic relationship with the first generation. The relationship existing 

 between sporophytic and gametophytic generations may be considered 

 symbiotic in nature even though the two generations are parts of the 



