MALADIE ET SYMBIOSE 285 



metabolism furnishes a bio-economically desirable surplus 

 product, i.e., one capable, inter alia, of stimulating progressive 

 evolution amongst animals. Whether or no the vegetable meta- 

 bolism is to be fruitful in bio-economic good effects, depends 

 largely upon the feeding habits and the connected " industries " 

 of the plants. Unless these are of a socio-physiologically high 

 order, there can be no valuable surpluses of metabolism. 



For in Nature, as in human life, all real values are based 

 upon labour ; and, here as there, it is all-essential that the 

 organism earn its living and discharge its obligations by adequate 

 service. It is considerations such as these that have been far too 

 long disregarded in biological philosophy. 



Darwin states : 



It is in perfect accordance with the scheme of nature, as worked out 

 by natural selection, that matter excreted to free the system from super- 

 fluous or injurious substances should be utilised for highly useful purposes. 



I should say, however, that the usefulness here entailed is 

 one in accordance with a scheme of definite service between 

 organism and organism, of " Symbiosis : Organic and Social," 

 of which scheme, in the words of Prof. Patrick Geddes, neither 

 Economist nor Naturalist has hitherto been able to provide an 

 outline. 



Darwin continues thus : 



To give an example in strong contrast with our present subject, the 

 larvae of certain beetles (Cassidae, etc.), use their own excrement to make 

 an umbrella-like protection for their tender bodies. 



Certainly these larvae have a curious way of providing for 

 their swaddling clothes ; their case, however, furnishes but poor 

 illustration of the contrast which ought here to have been shown 

 though this would have amounted to a relegation of " Natural 

 Selection " to the lumber-room of exploded scientific theories. 

 The contrast that should have been shown is that between a 

 healthy and a morbid circle of affinities, based upon a good and 

 a bad metabolism respectively. To provide a few examples of 

 a morbid circle of affinities : there are a number of relations 

 between animals of different species, coming under the .head of 

 " Commensalism," which are apt to degenerate into a kind of 

 social disease comparable to that of alcoholism amongst men. 

 The ants, for example, may become so " drunk " with the excretions 

 of some of their commensals and so intent upon the gratification, 

 that they neglect their social duties, and even suffer their own 



