SYMBIOSIS 69 



Privilege and duties in nature are normally according to 

 qualification and values, and we further see from this example 

 that reproduction itself is normally subservient to bio-economic 

 purposes. No matter how startling the mathematical possi- 

 bilities of reproduction per se may be, no species obtains more 

 scope than is warranted by its bio-economic usefulness. 

 The first consideration of life is that the work of 

 the world shall be done, and not that the mere repro- 

 duction of every species of organism shall continue without 

 limit. Symbiogenesis rather than mere multiplication is the 

 desideratum. So long as organisms continue strenuous, the 

 material for reproduction and for variation is always provided, 

 but reproduction may, if redundant, mean a mere waste of capital. 

 The problem of the lichen is how to produce ample capital 

 for survival purposes which, as this case so beautifully illus- 

 trates, is inseparably connected with bio-economic purposes 

 under external conditions which render the provision of capital 

 by each singly or by the ordinary method of unattached 

 biological symbiosis practically impossible. This calls for a 

 sufficiency of sympathy of purpose, of metabolic and bio- 

 economic compatibility and of restraint and mutual for- 

 bearance. Both partners must be willing to sacrifice some of 

 the independence which is entailed by the more usual form of 

 (unattached) biological symbiosis. The alga restrains its own 

 reproductive tendencies already moderate in view of the 

 relatively great amount of vitality deputed to its photo- 

 synthetic activities and this, not because of sterility or 

 parasitic over-adaptation or parasitic atrophy, but in obedience 

 to the principles of reciprocal differentiation requiring 

 mutual sacrifice and, in particular, sacrifice of the lower for 

 the higher. The fungus, in view of its bio-chemical equip- 

 ment, is the better qualified of the two for the communal 

 labours of sex, and therefore the alga plays, as the 

 Encyclopaedia Britannica article says, a subordinate part, but 

 it retains its own sexual faculties and remains capable of 

 reproducing- its kind when separated. 



