THE WEAK SIDES OF NATURAL SELECTION. 63 



more frequently than their weaker brethren, from the mere 

 fact that they are more venturesome, and hence more likely 

 to be on the wing. The effects of the co-existence of grouse 

 and falcons in any country, will, therefore, not be so much 

 the development of a strain of the former better adapted for 

 rapid flight, ultimately in the course of many generations 

 endowed with longer or more pointed wings, but merely a 

 thinning of numbers which will tell equally upon the strong 

 and upon the weak, and which in some instances may even 

 give an advantage to the latter. 



The argument of the influence of the falcon upon the 

 development of the grouse seems applicable not merely to 

 this individual instance, but to every case where a bird or a 

 beast has to struggle for existence against enemies greatly 

 its superiors in speed, in strength, or in cunning. Slight 

 increments in swiftness or force, trifling improvements in 

 offensive or defensive arms or in means of concealment must, 

 under many circumstances, be absolutely thrown away. 

 Thus there are numbers of cases where preservation and 

 destruction are not necessarily selective. 



Nor can we admit that existing species are universally and 

 necessarily ennobled by the " Struggle for Existence." It is 

 well known that when a man is seeking to improve any 

 cultivated plant or domestic animal, his first step is to sup- 

 press all struggle for existence, whether with other species 

 or among co-existing individuals of the same species. The 

 gardener plants on a given plot of ground only so many 

 trees, etc., as may find a superabundance of nutrient matter, 

 of air and light. As far as it lies in his power he eliminates 

 all struggle with weeds, or animal competitors. And his 

 results, gathered not by theory, but purely by experience, 

 prove that he is right. Imagine a competitive turnip-field 

 where the plants are left, in vulgar phrase, to " fight it out." 

 The experience of slovenly farmers has proved that such a 

 field will produce neither any fine roots, nor a total average 

 crop equal to that of a field where the struggle for existence 

 has been suppressed. If the weaker individuals finally go 

 to the wall in this struggle, it has first called them into 

 existence. 



There is yet a further general consideration to be weighed. 

 Mr. A. R. Wallace in his " Island Life" (p. 55) admits that 

 " new species can only be formed when and where there is 

 room for them." Hence the less severe the struggle for 

 existence, or in other words the less Natural Seleetiou is 



