VOL. I.] The Economy of Nature. 35 



+ 



the little thing. Gradually the insect became less rare, and as soon 

 as a sufficient number of shotguns were placed in the hands of little 

 boys who shot httle birds, I had ample opportunities to fill the 

 empty spot in my collection that for several years had only the male 



of the species on a pin. 



I have counted four generations of the insect in one summer. 

 Nevertheless they did not endanger the life of the trees inhabited 

 by them. There existed still a sufficient number of insect-feeding 

 birds to decimate the four broods of the insect, especially a species 

 of titmouse, then rather common in our surroundings and very fre- 

 quent in Marin county, took care of the eggs and the adult cater- 

 pillar. This bird managed in some way to escape destruction by 

 the shotgun, but then the English sparrow was introduced by some 

 well-meaning but imperfecdy instructed people. The sparrow soon 

 drove away the titmouse. The titmouse no more decimated the 

 Phryganidia ^^^ and larva, at both of which the sparrow looked 

 with a contemptuous smile. The Phryganidia multiplied in mathe- 

 matical progression; the leaves of the live oaks, for instance at San 

 Rafael, disappeared four times a summer ; some trees survived, 

 others succumbed; and so you see the introduction of the English 

 sparrow destroyed our Californian live oaks. The best proof that 

 the English sparrow was the cause of this destruction is the circum- 

 stance that the destruction coincides with the spreading of the 

 sparrow. The sparrow being an admirer of human civilization, 

 never moves from the neighborhood of cities as long as he can 

 help, but extends baneful influence on the rest of the birds, unfortu- 

 nately, over a more considerable area than that which he really 



occupies himself 



The phenomena referred to show very clearly that an interference 

 in any province of biology does not remain a single interference, 

 but like a stone thrown into a pond raises circles of disturbance ex- 

 tending farther and farther, till at last nature restores a state of 

 things more or less like the one that was suspended by the original 



interference. 



The same state of things never returns, because nature never 

 copies herself; she is progressive. Changes are constantly going 

 on in the form of slow development. If I say slow development of 

 course I speak from my own standpoint, or better, from the stand- 

 point of our race, because nature does not know the ideas of slow 

 and rapid, because the universe knows neither space nor time. 



