RIGHT-HANDEDNESS AND LEFT-HAN.DEDNESS. 257 



the species be considered a useful character, though it is persistently 

 inherited. 



Standing near me is a flower-pot, in which are several stalks of the 

 common calla (I believe the botanical name is Richardia (ethiopica) in 

 bloom ; and a little inspection shows that each spathe and leaf-bud is 

 twisted in the same way. If the leaf is held with the point up and the 

 upper surface toward you, the half of the leaf on your left is the part 

 that formed the inside of the leaf -bud, and the margin of the leaf on 

 your right is the part that formed the outside of the leaf-bud. This 

 character is quite persistent in the specimens of this species found in 

 this city, though I am told that a leaf twisted in the opposite way 

 sometimes appears ; while in the distinct species popularly called the 

 black calla I believe the character is reversed. Now, does this 

 persistence prove that the character in question is essential to the 

 welfare of the species? Are we justified in assuming that natural 

 selection is the cause of the persistence of such characteristics? Can 

 anyone throw light on the subject that will make it easier to believe 

 that the adaptation of the species would be in the least impaired if all 

 the leaves and spathes were twisted in the reverse way? 



The usual method of meeting the natural inference from such cases is 

 based on a double assumption, the first part of which is that natural 

 selection is the only intelligible explanation of the modification of 

 species or the persistence of character that has ever been given, and 

 that if in any case we abandon this explanation, it is equivalent to 

 abandoning all explanation ; the second part of the assumption being 

 that it is simply our ignorance of the facts that prevents us from 

 recognizing the life-preserving results that are gained by the char- 

 acteristic in question. This assumption ignores both the fact that 

 species presenting characters of the kind referred to are found on 

 every side, indeed that almost every species that fails to maintain com- 

 plete symmetry of form is an example, and the fact that Darwin him- 

 self pointed out another principle besides natural selection producing 

 persistent characters. This principle of sexual selection he carefully 

 distinguished from natural selection, showing that the results 

 produced by it could never be produced by natural selection, and 

 even maintaining that "It is not surprising that a slightly injurious 

 character should have been thus acquired." (The Descent of Man, 

 2d ed., p. 601.) 



For my part I do not think much progress can be made in dis- 

 covering where natural selection is the chief agent and where it is not 

 the chief agent till we have carefully defined what we mean by utility 

 and natural selection, and then adhere to our definitions. In my 



