164 Instinct, 



the work to completion, correspond with the changes 

 in the inorganic world and vegetable kingdom. 



These general adaptations of living things to 

 the changes of the earth, and the correlation of the 

 changes among the different orders of living things 

 are much more common and marked than is gener- 

 ally supposed. Every change seems to be a part 

 of a series of machinery adjusted and set in motion 

 according to a plan ; and such a plan, that every 

 wheel must move with a given velocity, and start 

 and stop at a given time, or loss and ruin follow. 



But in addition to these general adaptations, by 

 which all beings in the world seem to be more or 

 less dependent upon others, there are certain spe- 

 cial relations of animals to plants and of animals 

 to each other, secured by Instinct, that strike 

 us in the same manner, as special structure in 

 animals and plants themselves. There is a whole 

 tribe of insects, to which we have before referred, 

 that make galls upon plants, or check the growth 

 of the axis of plants in some peculiar manner. The 

 Gall-fly deposits an &gg upon the leaf or twig, ac- 

 cording to her habit ; and then her work ceases. 

 Now the tree takes up the work — forms a house for 

 the young insect and provides it with food ; until, 

 at last, the perfect insect makes its way through 

 the walls of the house, into the open air. This is 

 an entirely different thing from those many cases, 

 where the ^g% is simply deposited so that the young 

 can find proper food ; as in the case of the Tent- 

 moth, that deposits eggs upon Apple or Cherry 

 twigs ; or of the Carrion-fly, which deposits her eggs 



