ANIMAL MIGRATIONS 383 



ences, and there were no animals to aid in their 

 reproduction, to feed upon them, to dispose of their 

 dead carcasses, etc., the dominant forms would 

 doubtless be quite different from what they are 

 now. Darwin has shown by an admirable series of 

 observations how necessary insect agency is to the 

 fertilisation of the flowers of many plants. Hence 

 the organs of those insects and the parts of the 

 flowers have been (and are being) continually 

 modified, or moulded, the one on the other. I can 

 conceive that if certain Orchids were henceforth 

 entirely freed from the visits of insects, their flowers, 

 notwithstanding the apparent permanence of in- 

 herited (though now useless) peculiarities, would 

 immediately tend to revert to the symmetry which 

 no doubt they possessed in the remote types. I 

 have a good deal of evidence to show that in 

 tropical countries many peculiarities of structure in 

 the leaves and other parts of plants (prevailing 

 through large suites of species and genera) have 

 been brought about, and are still in part maintained, 

 by the unremitting agency of insects, especially of 

 Ants. These and many other matters require the 

 fullest investigation before the precise relations of 

 the changes, in animals and plants, that are taking 

 place under our eyes, can be properly understood 

 and appreciated. 



