104 SYMBIOSIS 



non-symbiotic associations. One might, in a sense, regard the 

 lichen as a hybrid between a fungus and an alga. This association, 

 because of its great bio-economic usefulness, has the fullest 

 sanction of Nature, which fact is expressed in health and in every 

 kind of viability without any symptom of " sterility of hybrids." 

 Everything in nature thus depends upon discriminative, i.e., 

 " right " association. 



The " atomic spark of memory," spoken of by Butler, is 

 safely supplied in Nature by symbiotic stimuli, in the case 

 of the animal, for instance, by plant-manufactured Vitamines, 

 which Dr. Funk, their discoverer, regards as the mother-sub- 

 stance of ferments and hormones, i.e., the regulators of health, 

 of growth and of reproduction. 



Once the physiological connections are understood, we shall 

 cease to over-emphasise, with Butler, the merely psychological 

 factor, and to expect too much from a mere artificial cross. 

 Nature cannot be supposed to be after mere crossing or mere 

 multiplication, any more than after mere modification or mere 

 " familiarity." Nature is after values in the widest sense of 

 the word. The most desirable " familiarity " in Nature is that 

 between symbiotic partners, which complement but do not 

 devour each other, and in so doing are able to form permanent 

 and lastingly fruitful intimacies. 



A writer so conscientious as Butler does not hesitate to admit 

 failures of theory. He would have considered it more parti- 

 cularly to the glory of his mnemic theory, had it accounted 

 satisfactorily for the difficulties presented by the problems of 

 hybridisation which so greatly puzzled Darwin. Whilst examin- 

 ing Darwin's account of these difficulties, Butler concedes that 

 his mnemic theory appears inadequate. 



This is one of Darwin's statements from Plants and A nimals 

 under Domestication, referred to by Butler : 



Finally, we must conclude, limited though the conclusion is, that 

 changed conditions of life have an especial power of acting injuriously on 

 the reproductive system. The whole case is quite peculiar, for these organs, 

 though not diseased, are thus rendered incapable of performing their 

 proper functions, or perform them imperfectly. 



This guarded statement shows the difficulties Darwin had 

 with hybridisation all the greater as the rationale of health 

 and of disease was not clearly seen or defined in his day. We 

 have seen, however, that incapacity of an organ to perform 



