64 SYMBIONTICISM AND THE ORIGIN OF SPECIES 



instance it lends itself to greater ultimate clarity to enlarge 

 and re-define the significance of a term, rather than intro- 

 duce an entirely new word to replace the old. 



A number of authors (Buchner, Nuttall, Cleveland, 

 Meyer and others) have recently discussed the propriety 

 of the term "sjTiibiosis" in connection with particular life 

 relationships. These discussions have been based upon 

 the original definition of symbiosis as given by De Bary, 

 in which the idea of mutual advantage is implied. Other 

 writers (Geddes, Thomson, Farmer, Wallin, Castellani 

 and others) appear to have sensed an underlying principle 

 in the various types of life relationships, and do not draw 

 a sharp distinction between symbiosis and parasitism. 



If we should retain the narrower conception of "mutual 

 advantage" in symbiosis, then it follows that we must 

 limit the term to those chance relationships in which 

 ''benefit" happens to be an accompaniment to both sym- 

 bionts. It is often most difficult to determine the nature 

 of the advantage gained by a symbiont. From the recent 

 discussions on symbiosis one gathers the impression that 

 there is an element of choice exercised by the symbionts. 

 Thus to quote Meyer ('25), 



From the experiments and the findings reported, it is easy to 

 assume that the mollusks derive some benefit from the intracellu- 

 lar bacteria as anabolists or catabolists of metabolic waste 

 products, but, what possible benefit can the microorganism derive 

 from the association? .... The recent literature on "symbio- 

 sis" has been carefully searched for other examples, but only 

 theories have been found which are not established on any scien- 

 tific basis. The function of the microscopic "symbiotes" and 

 their benefit to the host are explained, but little or nothing is 

 said regarding the possible advantages to the microorganisms. 

 .... Buchner's suggestion that the intracellular organisms 

 are benefited by being protected within the host from the drastic 

 atmospheric influences of heat, cold, desiccation, etc., is a trifle 

 unreasonable. 



