VII.] THE FERAL EQUILIBRIUM. l8l 



never heard of apple-scab, black-rot, downy -mildew, 

 leaf-blight, and a score of other plagues which now 

 haunt the orchards by day and the dreams by night. 

 In those blessed days, if the potatoes rotted it was laid 

 to the moon, and that was the end of it. It is strange 

 that so innocent a person as the -man -in -the -moon 

 should have had so many hard things said against 

 him ! 



Now, this whole problem of the increase of certain 

 kinds of insects and fungi belongs entirely to the inter- 

 relations of natural objects, — to insects and plants and 

 animals, and even man himself. If all natural forces 

 and conditions were always equal and unvarying, there 

 would be stability in all forms of life; but just so soon 

 as pressure is removed in any direction do all animals 

 and plants, directly or indirectly and in varying de- 

 grees, attempt to fill the breach. It is perfectly 

 apparent, upon a moment's thought, that this pressure 

 exists. The earth is now covered with plants and 

 animals. There is not room for many more. The, 

 world is not big enough to hold all the possible im- 

 mediate offspring of the animals and plants now living 

 upon it. One of the large trees in this city will bear 

 enough seeds in one year to make Indianapolis a 

 forest. So the greater part of the potential offspring 

 of any generation of living objects is destined either 

 not to start into independent growth or to die long 

 before maturity. One can not put ten cats in a bag 

 that will hold but nine, and if there is a hole in the 

 bag every cat will scramble for it. There is something 

 like an equilibrium in any perfectly wild region; the 

 place may be said to be full. But if man cuts off the 

 forest or destroys the animals, other plants and animals 



