98 Evolution and Adaptation 
of the wild Dipsacus; and this amount of change may have 
suddenly arisen in a seedling. So it has probably been with 
the turnspit dog; and this is known to have been the case 
with the ancon sheep. But when we compare the dray- 
horse and race-horse, the dromedary and camel, the various 
breeds of sheep fitted either for cultivated land or mountain 
pasture, with the wool of one breed good for one purpose, 
and that of another breed for another purpose; when we 
compare the many breeds of dogs, each good for man in 
different ways; when we compare the game-cock, so pertina- 
cious in battle, with other breeds‘so little quarrelsome, with 
‘everlasting layers’ which never desire to sit, and with the 
bantam so small and elegant; when we compare the host 
of agricultural, culinary, orchard, and flower-garden races 
of plants, most useful to man at different seasons and for 
different purposes, or so beautiful in his eyes, we must, I 
think, look further than to mere variability. We cannot 
suppose that all the breeds were suddenly produced as per- 
fect and as useful as we now see them; indeed, in many 
cases, we know that this has not been their history. The 
key is man’s power of accumulative selection: nature gives 
successive variations; man adds them up in certain direc- 
tions useful to him. In this sense he may be said to have 
made for himself useful breeds.” 
Darwin also gives the following striking examples, which 
make probable the view that domestic forms have really 
been made by man selecting those variations that are useful 
to him :— 
“In regard to plants, there is another means of observing 
the accumulated effects of selection — namely, by comparing 
the diversity of flowers in the different varieties of the same 
species in the flower-garden; the diversity of leaves, pods, 
o. tubers, or whatever part is valued, in the kitchen-garden, 
in comparison with the flowers of the same varieties; and 
the diversity of fruit of the same species in the orchard, in 
