202 THE ORIGIN OF SPECIES 



afforded for enlarging a little on gradations of structure, often as- 

 sociated with strange functions — an important subject, which was 

 not treated at sufficient length in the former editions of this work. 

 I will now briefly recapitulate the foregoing cases. 



With the giraffe, the continued preservation of the individuals 

 of some extinct high-reaching ruminant, which 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- 

 ordination. With the many insects which imitate various objects, 

 there is no improbability in the belief that an accidental resem- 

 blance to some common object was in each case the foundation for 

 the work of natural selection, since perfected through the occa- 

 sional preservation of slight variations which made the resem- 

 blance 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 per- 

 fect 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 favorable 

 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 teeth, then 

 partly as teeth and partly as a sifting apparatus, and at last al- 

 most exclusively for this latter purpose. 



With such structures as the above lemallae 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 

 continued use, together with inheritance. With respect to the mam- 

 mae of the higher animals, the most probable conjecture is that 

 primordially the cutaneous glands over the whole surface of a 

 marsupial sack secreted a nutritious fluid; and that these glands 

 were improved in function through natural selection, and concen- 

 trated into a confined area, in which case they would have formed 

 a mamma. There is no more difficulty in understanding how the 

 branched spines of some ancient Echinoderm, which served as a 



