214 OBJECTIONS TO THE THEOEY [CHAP. VI 



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 animals in a state of nature occasionally become 

 sterile; and if such insects had been social, and it had been 

 profitable to the community that a number should have been 

 annually born capable of work, but incapable of procreation, I 

 can see no especial difficulty in this having been effected through 

 natural selection. But I must pass over this preliminary difficulty. 

 The great difficulty lies in the working ants differing widely from 

 both 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 as instinct alone is concerned, the 

 wonderful difference in this respect between the workers and the 

 perfect females, would have been better exemplified by the hive- 

 bee. If a working ant or other neuter insect had been an ordinary 

 animal, I should have unhesitatingly assumed that all its 

 characters had been slowly acquired through natural selection; 

 namely, by individuals having been born with slight profitable 

 modifications, which were inherited by the offspring; and that 

 these again varied and again were selected, and so onwards. But 

 with the working ant we have an insect differing greatly from its 

 parents, yet absolutely sterile ; so that it could never have 

 transmitted successively acquired modifications of structure or 

 instinct to its progeny. It may well be asked how is it possible 

 to reconcile this case with the theory of natural selection 1 



First, let it be remembered that we have innumerable instances, 

 both in our domestic productions and in those in a state of nature, 

 of all sorts of differences of inherited structure which are corre- 

 lated with certain ages, and with either sex. We have differences 

 correlated not only with one sex, but with that short period when 

 the reproductive system is active, as in the nuptial plumage of 

 many birds, and in the hooked jaws of the male salmon. We 

 have even slight differences in the horns of different breeds of 

 cattle in relation to an artificially imperfect state of the male sex; 

 for oxen of certain breeds have longer horns than the oxen of other 

 breeds, relatively to the length of the horns in both the bulls and 

 cows of these same breeds. Hence I can see no great difficulty in 

 any character becoming correlated with the sterile condition of 

 certain members of insect-communities : the difficulty lies in 



