392 ON THE ORIGIN OF SPECIES 



parts being perhaps very simple in form ; and then 

 natural selection, acting on some originally created 

 form, will account for the infinite diversity in structure 

 and function of the mouths of insects. Neverthless, it 

 is conceivable that the general pattern of an organ 

 might become so much obscured as to be finally lost, by 

 the atrophy and ultimately by the complete abortion of 

 certain parts, by the soldering together of other parts, 

 and by the doubling or multiplication of others, — varia- 

 tions which we know to be within the limits of possi- 

 bility. In the paddles of the extinct gigantic sea-lizards, 

 and in the mouths of certain suctorial crustaceans, 

 the general pattern seems to have been thus to a certain 

 extent obscured. 



There is another and equally curious branch of the 

 present subject ; namely, the comparison not of the 

 same part in different members of a class, but of the 

 different parts or organs in the same individual. Most 

 physiologists believe that the bones of the skull are 

 homologous with — that is correspond in number and in 

 relative connection with — the elemental parts of a cer- 

 tain number of vertebrae. The anterior and posterior 

 limbs in each member of the vertebrate and articulate 

 classes are plainly homologous. We see the same 

 law in comparing the wonderfully complex jaws and 

 legs in crustaceans. It is familiar to almost every one, 

 that in a flower the relative position of the sepals, 

 petals, stamens, and pistils, as well as their intimate 

 structure, are intelligible on the view that they consist 

 of metamorphosed leaves, arranged in a spire. In 

 monstrous plants, we often get direct evidence of the 

 possibility of one organ being transformed into another; 

 and we can actually see in embryonic crustaceans and 

 in many other animals, and in flowers, that organs, 

 which when mature become extremely different, are at 

 an early stage of growth exactly alike. 



How inexplicable are these facts on the ordinary 

 view of creation ! Why should the brain be enclosed 

 in a box composed of such numerous and such extra- 

 ordinary shaped pieces of bone? As Owen has remarked, 



