16 On Some Interactions of Organisms. 



ary (parasites, for instance), — that while the destruction of 

 the latter would cause injurious oscillations in the species 

 aifected by them, they afford a very uncertain safeguard 

 against the rise of such oscillations. In fact, their undue 

 increase would be finally as dangerous as their diminution. 



Notwithstanding the strong presumption in favor of the 

 natural system, when we remember that the purposes of 

 man and what, for convenience' sake, we may call the pur- 

 poses of Nature do not fuller harmonize, we find it incredi- 

 ble that, acting intelligently, we should not be able to 

 modify existing arrangements to our advantage, — espe- 

 cially since much of the progress of the race is due to such 

 modifications made in the past. 



We should observe, in passing, that the principal general 

 problem of economic biology is that of the discovery of 

 the laws of oscillation in plants and animals, and of the 

 methods of Nature for its prevention and control. 



For all this, evidently, the first, indispensable requi- 

 site is a thorough knowledge of the natural order^ — an in- 

 telligently conducted natural history survey. Without the 

 general knowledge which such a survey would give us, all 

 our measures must be empirical, temporary, uncertain, 

 and often dangerous. 



Next we must know the nature, extent, and most im- 

 portant consequences of the disturbances of this order 

 necessarily resulting from human interference, — we must 

 study the methods by which Nature reduces these disturb- 

 ances, and learn how to second her efforts to our own best 

 advantage. 



But far the most important general conclusion we have 

 reached is a conviction of the general beneficence of Na- 

 ture, a profound respect for the natural order, a belief 

 that the part of wisdom is essentially that of practical con- 

 servatism in dealing with the system of things by which 

 we are surrounded. 



Suminary. 



The argument and conclusions of this paper may be thus 

 briefly recapitulated : — 



We find a mutual interdependence of organic groups and 



