230 OBJECTIONS TO THE TIIEOPwY Chap. VII. 



high ; but wc must suppose that the larger workmen had heads 

 four instead of three times as l:)ig as those of the smaller men, 

 and jaws nearly five times as big. The jaws, moreover, of the 

 working ants of the several sizes differed wonderfully in shape, 

 and in the form and number of the teeth. But the important 

 fact f(^r us is, that, though the workers can be grouped into castes 

 of different sizes, yet they graduate insensibly into each other, 

 as does the widely-different structure of their jaws. I speak 

 confidently on this latter point, as Sir J. Lubbock made draw- 

 ings for me, with the camera lucida, of the jaws which I dis- 

 sected from the workers of the several sizes. Mr. Bates, in his 

 most interesting "Naturalist on the Amazons," has described 

 analogous cases. 



With these facts before me, I believe that natural selection, 

 by acting on the fertile ants or parents, could form a species 

 which should regularly produce neuters, either all of large size 

 with one form of jaw, or all of small size M-ith jaws having a 

 Avidely-different structure; or lastl}^, and this is the clima.x of 

 dilliculty, one set of workers of one size and structure, and at 

 the same time another set of workers of a different size and 

 structure ; a graduated series having first been formed, as in 

 the case of the driver-ant, and then the extreme forms having 

 been produced in greater and greater numbers, through the 

 survival of the parents which generated them, until none with 

 an intermediate structure were produced. 



An analogous explanation has been given by Mr. Wallace, 

 of the equally com[)lcx case, of certain Malayan butterflies 

 regularly appearing under two or even three distinct female 

 forms ; and by Fritz Miiller, of certain Brazilian crustaceans 

 likewise appearing under two widely-distinct male forms. But 

 this subject need not here be discussed. 



I have now explained how, as I believe, the wonderful fact 

 of two distinctly-defined castes of sterile workers existing in 

 the same nest, both widely different from each other and from 

 their parents, has originated. We can see how useful their 

 production niay have been to a social comnnmity of ants, on 

 the same, principle that the division of labor is useful to civil- 

 ized man. Ants, however, work by inherited instincts and by 

 inherited organs or tools, while man works by acquired knowl- 

 edge and manufactured instruments. But I must confess, that, 

 Avith all my faith in natural selection, I should never have an- 

 ticipated tiiat this principle could have been efficient in so high 

 a degree, had not the case of these neuter insects convinced me 



