294 ORIGIN OF SPECIES 



munity, and those males and females had been continually 

 selected, which produced more and more of the smaller 

 workers, until all the workers were in this condition; we 

 should then have had a species of ant with neuters in nearly 

 the same condition as those of Myrmica. For the workers of 

 Myrmica have not even rudiments of ocelli, though the male 

 and female ants of this genus have well-developed ocelli. 



I may give one other case: so confidently did I expect 

 occasionally to find gradations of important structures be- 

 tween the different castes of neuters in the same species, that 

 I gladly availed myself of Mr. F. Smith's offer of numerous 

 specimens from the same nest of the driver ant (Anomma) 

 of West Africa. The reader will perhaps best appreciate the 

 amount of difference in these workers, by my giving not the 

 actual measurements, but a strictly accurate illustration: the 

 difference was the same as if we were to see a set of work- 

 men building a house, of whom many were five feet four 

 inches high, and many sixteen feet high; but we must in 

 addition suppose that the larger workmen had heads four 

 instead of three times as big 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 for us is, that, though the workers can be 

 grouped into castes of different sizes, yet they graduate in- 

 sensibly into each other, as does the widely-different struc- 

 ture of their jaws. I speak confidently on this latter point, 

 as Sir J. Lubbock made drawings for me, with the camera 

 lucida, of the jaws which I dissected from the workers of 

 the several sizes. Mr. Bates, in his interesting 'Naturalist on 

 the Amazons,' has described analogous cases. 



With these facts before me, I believe that natural selec- 

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

 species which should regularly produce neuters, all of large 

 size with one form of jaw, or all of small size with widely 

 different jaws; or lastly, and this is the greatest difficulty, 

 one set of workers of one size and structure, and simultane- 

 ously another set of workers of a different size and struc- 

 ture ; — a graduated series having first been formed, as in the 

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



