356 OBJECTIONS TO THE THEOKY [Chap. VEI. 



tions are known to exist; cases of instincts of such 

 trifling importance, that they could hardly have been 

 acted on by natural selection ; cases of instincts almost 

 identically the same in animals so remote in the scale of 

 nature, that we cannot account for their similarity by 

 inheritance from a common progenitor, and consequently 

 must believe that they were independently acquired 

 through natural selection. I will not here enter on these 

 several cases, but will confine myself to one special 

 difficulty, which at first appeared to me insuperable, 

 and actually fatal to the whole theory. I allude to the 

 neuters or sterile females in insect-communities; for 

 these neuters often differ widely in instinct and in 

 structure from both the males and fertile females, and 

 yet, from being sterile, they cannot propagate their 

 kind. 



The subject well deserves to be discussed at great 

 length, but I will here take only a single case, that of 

 working or sterile ants. How the workers have been 

 rendered sterile is a difficulty ; but not much greater 

 than that of any other striking modification of structure ; 

 for it can be shown that some insects and other articulate 

 animal? in a state of nature occasionallv become sterile ; 

 and if such insects had been social, and it had been pro- 

 fitable to the community that a number should have 



en annually born capable of work, but incapable of 

 procreation, I can see no -special difficulty in this having 

 n effected through natural selection. But I must 

 pass over this preliminary difficulty. The great diffi- 

 culty lies in the working ants differing widely from 

 1 x>th the males and the fertile females in structure, as 

 in the shape of the thorax, and in being destitute of 

 wings and sometimes of eyes, and in instinct. As far 



