4 On Some Interactions of Organisms. 



terdependence of its parts, on the other hand, it differs 

 from the single animal in the fact that, notwithstanding 

 this intimate and instant sympathy of part with part, it 

 has an immense vitality. To cut off the leg of an ani- 

 mal is often sufficient to destroy its life, but one might 

 cut off the head of the animal world, so to speak, without 

 seriously impairing its energy. Suddenly to annihilate 

 every living vertebrate would doubtless set on foot some 

 tremendous revolutions in the life of the earth, but it is 

 certain that in time the wound would heal, — that Nature 

 would finish by readjusting her machinery and would then 

 go on much as before. In fact, any subkingdom of ani- 

 mals or any class of plants might thus be struck out, with, 

 out the slightest danger that terrestrial life would perish 

 as a consequence. The functions of the missing member 

 would be taken on in part by other members, and in part 

 be rendered needless by new adjustments. 



We see many present illustrations of this fact, as in 

 Australia, where there is but one native carnivorous ani- 

 mal, and that probably not indigenous ; in several Pacific 

 islands where mammals are unknown ; and in New Zealand 

 and the Galapagos, where insects are extremely few and 

 the flowers, therefore, chiefly colorless and odorless. We 

 see, likewise, illustrations of the same truth in the condi- 

 tions of vegetable and animal life in earlier geological pe- 

 riods. Plants and insects, for example, existed together 

 through vast periods of time when there were neither 

 mammals nor birds on earth to supervise or regulate their 

 relations. 



If this is true of such immense and revolutionary dis- 

 turbances, it is all the more certain that this same spon- 

 taneous action of natural forces must in time reduce the 

 smaller disturbances of the primitive order caused every- 

 where by civilized man, and must end by adjusting the 

 whole scheme of organic relations to his interests as com- 

 pletely as to the interests of any other species. It is also 

 plain that if man understands clearly the disorders which 

 arise in the system of Nature as a result of the rapid pro- 

 gressive changes in his own condition and activities, and 

 understands also the processes of Nature which tend to 



