178 



THE ORIGIN OF SPECIES 



plants which have their several organs much modified 



and reduced in number as the highest. 



I If we take as the standard of high organization, the 



I amount of differentiation and specialization of the several 

 organs in each being when adult (and this will include 

 the advancement of the brain for intellectual purposes), 

 natural selection clearly leads toward this standard: for all 

 .physiologists admit that the specialization of organs, in- 

 jasmuch as in this state they perform their functions bet- 

 ter, is an advantage to each being; and hence the accu- 

 mulation of variations tending toward specialization is 

 within the scope of natural selection. On the other 

 ihand, we can see, bearing in mind that all organic 

 (beings are striving to increase at a high ratio and to 

 i seize on every unoccupied or less well occupied place 

 \ia the economy of nature, that it is quite possible for 

 'natural selection gradually to fit a being to a situation 

 in which several organs would be superfluous or useless: 

 ;in such cases there would be retrogression in the scale of 



\fbrganization. Whether organization on the whole has 

 actually advanced from the remotest geological periods 

 to the present day will be more conveniently discussed 

 in our chapter on Geological Succession. 



But it may be objected that if all organic beings thus 

 tend to rise in the scale, how is it that throughout the 

 world a multitude of the lowest forms still exist; and 

 how is it that in each great class some forms are far 

 more highly developed than others? Why have not the 

 more highly developed forms everywhere supplanted and 

 exterminated the lower? Lamarck, who believed in an 

 innate and inevitable tendency toward perfection in all 

 organic beings, seems to have felt this difficulty so 



