THEOHY OF NATURAL SELECTION, 235 



have shown, as I hope, that there is no great difliculty on 

 this head. A good opportunity has thus been alTorded for 

 enlarging a little on gradations of structure, often associ- 

 ated with strange functions — an important subject, which 

 was not treated at sufificient length in the former editions 

 of this work. I will now briefly recapitulate tlie foregoing 

 cases. 



With the giraffe, the continued preservation of tlie indi- 

 viduals of some extinct high-reaching ruminant, whicli had 

 the longest necks, legs, etc., and could browse a little 

 above the average height, and the continued destruction of 

 those which could not browse so high, would have sufficed 

 for the production of this remarkable quadruped; but the 

 prolonged use of all the parts, together with inheritance, 

 will have aided in an important manner in their co-ordina- 

 tion. With the many insects which imitate various ob- 

 jecii^, there is no improbability in the belief that an acci- 

 dental resemblance to some common object was in each case 

 the foundation for the work of natural selection, since per- 

 fected through the occasional preservation of slight variations 

 which made the resemblance at all closer; and this will have 

 been carried on as long as the insect continued to vary, 

 and as long as a more and more perfect resemblance led to 

 its escape from sharp-sighted enemies. In certain species 

 of whales there is a tendency to the formation of irregular 

 little points of horn on the palate; and it seems to be quite 

 within the scope of natural selection to preserve all favor- 

 able variations, until the points were converted, first into 

 lamellated knobs or teeth, like those on the beak of a 

 goose — then into short lamellae, like those of the domestic 

 ducks — and then into lamellae, as perfect as those of the 

 shoveller-duck — and finally into the gigantic plates of 

 baleen, as in the mouth of the Greenland whale. In the 

 family of the ducks, the lamellae are first used as teetli, 

 then partly as teeth and partly as a sifting apparatus, and 

 at last almost exclusively for this latter purpose. 



With such structures as the above lamella3 of horn or 

 whalebone, habit or use can have done little or nothing, as 

 far as we can judge, toward their development. On the 

 other hand^ the transportal of the lower eye of a flat- 

 fish to the upper side of the head, and the formation of a 

 prehensile tail, may be attributed almost wholly to con- 



