Harmonious Adaptation 35 



illustration to show how imposing the difference between the two 

 kinds of workers in one species would seem if we translated it into 

 human terms. In regard to the Driver ants (Anomma) we must 

 picture to ourselves a piece of work, "for instance the building of 

 a house, being carried on by two kinds of workers, of which one group 

 was five feet four inches high, the other sixteen feet high 1 ." 



Although the ant is a small animal as compared with man or with 

 the Irish Elk, the "soldier" with its relatively enormous jaws is 

 hardly less heavily burdened than the Elk with its antlers, and in 

 the ant's case, too, a strengthening of the skeleton, of the muscles, 

 the nerves of the head, and of the legs must have taken place parallel 

 with the enlargement of the jaws. Harmonious adaptation (co- 

 adaptation) has here been active in a high degree, and yet these 

 " soldiers " are sterile ! There thus remains nothing for it but to 

 refer all their adaptations, positive and negative alike, to processes 

 of selection which have taken place in the rudiments of the workers 

 within the egg and sperm-cells of their parents. There is no way out 

 of the difficulty except the one Darwin pointed out. He himself did 

 not find the solution of the riddle at once. At first he believed that 

 the case of the workers among social insects presented "the most 

 serious special difficulty" in the way of his theory of natural selection ; 

 and it was only after it had become clear to him, that it was not the 

 sterile insects themselves but their parents that were selected, 

 according as they produced more or less well adapted workers, that 

 he was able to refer to this very case of the conditions among ants 

 "in order to show the power of natural selection 2 ." He explains his 

 view by a simple but interesting illustration. Gardeners have pro- 

 duced, by means of long continued artificial selection, a variety of 

 Stock, which bears entirely double, and therefore infertile flowers 3 . 

 Nevertheless the variety continues to be reproduced from seed, 

 because, in addition to the double and infertile flowers, the seeds 

 always produce a certain number of single, fertile blossoms, and these 

 are used to reproduce the double variety. These single and fertile 

 plants correspond "to the males and females of an ant-colony, the 

 infertile plants, which are regularly produced in large numbers, to 

 the neuter workers of the colony." 



This illustration is entirely apt, the only difference between the 

 two cases consisting in the fact that the variation in the flower is not 

 a useful, but a disadvantageous one, which can only be preserved 

 by artificial selection on the part of the gardener, while the trans- 

 formations that have taken place parallel with the sterility of the 

 ants are useful, since they procure for the colony an advantage in 



1 Origin of Species (6th edit.), p. 232. 



3 Origin of Species, p. 233 ; see also edit. 1, p. 242. 3 Ibid. p. 230. 



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