232 ANCESTR Y AND CLA SSIFICA TION. 



of maxillae, these parts being very simple in 

 form : and then natural selection will account for 

 the infinite diversity in the structure and func- 

 tions" of the mouth in all insects. If, however, 

 we were to choose between biting and sucking, 

 there can be no doubt that the former is the more 

 primitive condition, since insects existed before 

 tubular flowers. 



We may then consider it probable that the 

 metamorphoses of the ancient butterfly were of 

 a very simple nature, and that the present alter- 

 ations of form, structure, and life have been grad- 

 ually induced. We have seen, even in the exist- 

 ing species, striking variations in form, color, and 

 period of appearance ; and in the divergence of 

 the present metamorphoses from those of the 

 past we have a signal proof of the same tendency 

 to variation, and of the magnitude which it may 

 attain ; in their earliest stages these variations 

 were probably confined to individuals, but gradu- 

 ally, by accretion and persistence, were impressed 

 upon the group. We may even see proofs of the 

 continued action of this tendency to change, of 

 the unstable equilibrium of the present condition 

 of things, of the pliability of structure and modes 

 of development, in a hypermetamorphosis, as it 

 may be called, which caterpillars undergo. The 

 extremities of the series of transformations in 

 butterflies are complete ; nothing can be simpler 



