ORIGIN OF ORGANIC FORMS 311 



for existence and its necessary outcome, the survival of 

 the fittest, or, as Darwin metaphorically puts it, natural 

 selection, is the necessary logical outcome of the law 

 of the rapid multiplication of organic forms. ^ Such 

 deductive proofs are not the only ones that can be 

 brought forward in support of the fact of the struggle 

 for existence and selection ; immediate observation 

 brings us to the same inference. We have only to take 

 a mixture of flower seeds, say of sweet peas of different 

 colour, and gather all the seeds each year and sow them 

 again on the same bed, to find in a few years' time that 

 some colours will oust the others from the bed. This 

 means that even such an insignificant character as colour 

 (most likely some property correlated with it, which 

 escapes our immediate observation) can decide the 

 victory in the struggle for existence. The same result is 

 observed in experiments in manuring natural meadows. 

 We have seen that nitrogenous manures and mineral salts 

 containing phosphoric acid and potassium constitute 

 beyond doubt useful and indispensable food for every 

 plant* But if we manure a natural meadow containing 

 a certain percentage of grasses and a certain percentage 

 of leguminous plants, we notice that when we use 

 exclusively nitrogenous manures the cereals get the 

 upper hand of the leguminous plants. On the other 

 hand, by using manures without nitrogen the advantage 

 is all on the side of the leguminous plants. Both 

 manures are useful for both kinds of plants, although 

 to a different degree, and according to that difference 

 the success in the struggle for existence falls to the one 

 or to the other. Lastly, as has been rightly observed, 



1 The metapliorical use of the word selection has led many critics 

 astray (as has been already mentioned) : they said that the very expression 

 ' selection ' points to the fact that Darwin was obliged to ascribe conscious 

 activity to Nature. If formerly it was only slow people who could be 

 led into this error, to-day, after the explanation given by Darwin, it 

 is only people unscrupulous in their choice of methods of argument who 

 can have recourse to such quibbling. 



