Schneider : the phenomena of symbiosis. 925 



tween what is usually designated as mere association of living 

 things and what constitutes true symbiosis. The nearness of 

 these relationships will become still more evident on attempt- 

 ing to define symbiosis. 



Definition of symbiosis. — Etymologically the word sym- 

 biosis signifies "a living together." It is therefore pecu- 

 liarly fitted for use in the broader sense, as including all 

 phenomena of "living together." Owing to the mutability and 

 imperfections of a language the etymology of a word is not 

 sufficient to limit its application. A careful definition or ex- 

 planation is always necessary. Symbiosis may be defined as a 

 contiguous association of two or more morphologically distinct 

 organisms, not of the same kind, resulting in a loss or acquisition 

 of assimilated food- substances. This definition is by no means 

 perfect. It will, however, be left to further discussions to 

 point out and explain its deficiency. 



The origin of symbiosis. — It is self-evident that before a sym- 

 biotic relationship between morphologically distinct organisms 

 could be established it was absolutely necessary that they be 

 brought in close proximity, or in actual contact. It is also 

 clear, from a priori reasoning, that there could be no inherent 

 tendency within these organisms to attract or repel each other; 

 nor could the first contact have been co-incident with morpho- 

 logical and physiological adaptations. The very conception 

 of symbiosis implies something secondary, and in a certain 

 sense something abnormal. The establishment of marked 

 symbioses required long periods of time; just when they began 

 is impossible to determine. It is, no doubt, justifiable to as- 

 sume that a number of lowly organized organisms existed in a 

 natural state, manifesting no symbiotic phenomena, because 

 competition (for space) had not yet resulted from over-pro- 

 ductiveness. It may also be assumed that symbiotic phenom- 

 ena began to manifest themselves during the earliest geologic 

 ages. All the multitudinous phenomena of antagonistic sym- 

 biosis, and of mutualistic symbiosis, are highly specialized 

 biological conditions which were initiated by the first contact 

 of morphologically distinct organisms. This contact produced 

 a change in the environment. An unforseen struggle was the 

 result, since it is reasonable to assume that the first relation- 

 ship of contiguous organisms was antagonistic rather than 

 mutualistic. As already indicated, organisms are not primar- 



