206 SELECTION. Chap. XX. 



I will conclude this chapter by some remarks on an im- 

 portant subject. With animals such as the giraffe, of which 

 the whole structure is admirably co-ordinated for certain pur- 

 poses, it has been supposed that all the parts must have been 

 simultaneously modified ; and it has been argued that, on the 

 principle of natural selection, this is scarcely possible. But in 

 thus arguing, it has been tacitly assumed that the variations 

 must have been abrupt and great. No doubt, if the neck 

 of a ruminant were suddenly to become greatly elongated, 

 the fore limbs and back would have to be simultaneously 

 strengthened and modified ; but it cannot be denied that an 

 animal might have its neck, or head, or tongue, or fore-limbs 

 elongated a very little without any corresponding modifica- 

 tion in other parts of the body ; and animals thus slightly 

 modified would, during a dearth, have a slight advantage, 

 and be enabled to browse on higher twigs, and thus survive. 

 A few mouthfuls more or less every day would make all the 

 difference between life and death. By the repetition of the 

 same process, and by the occasional intercrossing of the sur- 

 vivors, there would be some progress, slow and fluctuating 

 though it would be, towards the admirably co-ordinated 

 structure of the giraffe. If the short-faced tumbler-pigeon, 

 with its small conical beak, globular head, rounded body, 

 short wings, and small feet — characters which appear all in 

 harmony — had been a natural species, its whole structure 

 would have been viewed as well fitted for its life ; but in this 

 case we know that inexperienced breeders are urged to attend 

 to point after point, and not to attempt improving the whole 

 structure at the same time. Look at the greyhound, that 

 perfect image of grace, symmetry, and vigour ; no natural 

 species can boast of a more admirably co-ordinated structure, 

 with its tapering head, slim body, deep chest, tucked-up 

 abdomen, rat-like tail, and long muscular limbs, all adapted 

 for extreme fleetness, and for running down weak prey. 

 Now, from what we see of the variability of animals, and 

 from what we know of the method which different men follow 

 in improving their stock — some chiefly attending to one 

 point, others to another point, others again correcting defects 

 by crosses, and so forth — we may feel assured that if we 



