238 
INSTINCT. 
Chap. VII. 
desired end. Thus, a well-flavoured vegetable is cooked, 
and the individual is destroyed; but the horticulturist 
sows seeds of the same stock, and confidently expects to 
get nearly the same variety: breeders of cattle wish the 
flesh and fat to be well marbled together; the animal 
has been slaughtered, but the breeder goes with confi¬ 
dence to the same family. I have such faith in the 
powers of selection, that I do not doubt that a breed 
of cattle, always yielding oxen with extraordinarily long 
horns, could be slowly formed by carefully watching 
which individual bulls and cows, when matched, pro¬ 
duced oxen with the longest horns; and yet no one 
ox could ever have propagated its kind. Thus I believe 
it has been with social insects: a slight modification of 
structure, or instinct, correlated with the sterile condi¬ 
tion of certain members of the community, has been ad¬ 
vantageous to the community: consequently the fertile 
males and females of the same community flourished, 
and transmitted to their fertile offspring a tendency to 
produce sterile members having the same modification. 
And I believe that this process has been repeated, until 
that prodigious amount of difference between the fertile 
and sterile females of the same species has been pro¬ 
duced, which we see in many social insects. 
But we have not as yet touched on the climax of the 
difficulty; namely, the fact that the neuters of several 
ants differ, not only from the fertile females and males, 
but from each other, sometimes to an almost incredible 
degree, and are thus divided into two or even three 
castes. The castes, moreover, do not generally gra¬ 
duate into each other, but are perfectly well defined; 
being as distinct from each other, as are any two species 
of the same genus, or rather as any two genera of the 
same family. Thus in Eciton, there are working and 
soldier neuters, with jaws and instincts extraordinarily 
