THE LAW OF CONCORD IN NATURE 39 



plant, Dr. Russell tells us, does not accelerate the nitrate 

 formation. 



On the contrary, the growing plant appears to retard it, and nitrate 

 is always formed in higher quantities on fallow than on cropped land, even 

 after allowing for what is taken by the crop. 



Whatever the exact explanation may be, we may be sure 

 that the fact of Symbiosis necessarily introduces regulative and 

 restraining factors in many directions. It is quite intelligible 

 that the strenuous plant finds a surfeit of nutrients incompatible 

 with its work. It is only the harmful, i.e., the idle and predatory 

 organisms of the soil, that " thrive " in surfeit. These latter, 

 in Dr. Russell's words, given a continued spell of " favourable " 

 conditions (which I take to be conditions favouring surfeit) may 

 even establish " some sort of " superiority. Under the identical 

 conditions the efficiency of the strenuous bacteria falls off, and, 

 therefore, under a resulting double inadequacy of Symbiosis, 

 the plants must suffer. Dr. Russell would roughly divide the 

 soil population into two groups : one favourable to the pro- 

 duction of plant food, the other not. This shows that our 

 investigators are driven more and more to make that vital and 

 more generalised and more universal distinction which I have 

 set myself to emphasise, namely, between the symbiotic and the 

 non-symbiotic, the normal and the abnormal, modes of life 

 generally. The way to keep down the noxious, i.e., parasitic 

 population in cultivation consists in sterilisation of the soil. 



The useful population is, on the whole, more resistant to adverse cir- 

 cumstances than are the harmful organisms, and, therefore, survives more 

 drastic treatment. 



But, if the strenuous organisms are more resistant to adverse 

 circumstances than the parasitic ones, this is precisely because, 

 relying upon honest labour and on the support of Symbiosis, 

 they consequently enjoy better health and stronger constitutions 

 than those whose existence is not so supported. Parasitism, on 

 the other hand, as the economic antithesis to Symbiosis, must 

 make for the physiological antithesis, i.e., for weakness, disease 

 and retrogression, which is amply borne out by results in either 

 case. 



To give but one further example of the way in which Parasitism 

 shows itself incompatible with symbiotic support : the Nematode 

 worms, most of which are rank parasites, and which, according to 

 Prof. Arthur J. Thomson, " do not seem to lead on to anything 



