256 



THE WORLD OF LIFE 



CHAP. f 



(2) The Co-ordination of Variations 



The next difficulty, one which Herbert Spencer laid 

 much stress on, is, that every variation, to be of any use to 

 a species, requires a number of concurrent variations, often 

 in different parts of the body, and these, it is said, cannot be 

 left to chance. Herbert Spencer discussed this point at 

 great length in his Factors of Organic Evolution ; and, as 

 one of the illustrative cases, he takes the giraffe, whose 

 enormously long neck and forelegs, he thinks, would have 

 required so many concurrent variations that we cannot 

 suppose them to have occurred through ordinary variation. 

 He therefore argues that the inherited effects of use and 

 disuse are the only causes which could have brought it 

 about ; and Darwin himself appears to have thought that 

 such inheritance did actually occur. 



The points which Spencer mainly dwells upon are as 

 follows : The increased length and massiveness of the neck 

 would require increased size and strength of the chest with 

 its bones and muscles to bear the additional weight, and 

 also great additions to the strength of the forelegs to carry 

 such a burthen. Again, as the hind -legs have remained 

 short, the whole body is at a different angle from what it 

 was before the change from the ordinary antelope-type, and 

 this would require a different shape in the articulating joints 

 of the hips and some change in the muscles ; and this would 

 be the more important as the hind- and forelegs now have 

 unequal angular motions when galloping, involving changed 

 co-ordination in all the connected parts, any failure in which 

 would diminish speed and thus be fatal to the varying 

 individuals. Even the blood-vessels and nerves of these 

 various parts would require modifications exactly adapted to 

 the change in the other parts ; and he urges that any in- 

 dividuals in which all these necessary variations did not take 

 place simultaneously, would be at a disadvantage and would 

 not survive. To do his argument justice, I will quote one of 

 his most forcible paragraphs. 



"The immense change in the ratio of fore-quarters to hind- 

 quarters would make requisite a corresponding change of ratio in 

 the appliances carrying on the nutrition of the two. The entire 



