158 THE METHOD OF DARWIN. 



advantage to self is the only invariable motive 

 of all the striving in the universe. The moral 

 consequences of the theory seemed to outrage 

 all the noble ideals that had ever been cherished 

 in the world. 



Since the time he made the declaration, there 

 have been up for discussion numerous cases of 

 adaptation which seemed of no value, or even 

 hurtful, to the species possessing them. These 

 difficulties have caused a vast amount of stren- 

 uous explanatory wriggling under the name 

 symbiosis; but there has as yet been no case 

 found which can be positively regarded as an 

 example of what Darwin said could not exist. 

 He had long studied adaptations carefully; but 

 the nature of the cause, after he had discovered 

 it, helped him to understand more clearly the 

 nature of adaptations. 



Good testimony for the necessity of a theory 

 of some kind to enable him to work effectively 

 is what Darwin wrote to Asa Gray about 

 cleistogamic flowers, which are self-fertilized 

 and do not open at all. He said, "The tem- 

 porary theory which I have formed on this class 

 of dimorphism, just to guide experiment, is 

 that the perfect flowers can only be perfectly 

 fertilized by insects, and are in this case abun- 

 dantly crossed; but that the flowers are not 



