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