216 
INSTINCTS. 
Chap. VII. 
young pheasants, though reared under a hen. It is not 
that chickens have lost all fear, but fear only of dogs 
and cats, for if the hen gives the danger-chuckle, they 
will run (more especially young turkeys) from under 
her, and conceal themselves in the surrounding grass or 
thickets; and this is evidently done for the instinctive 
purpose of allowing, as we see in wild ground-birds, their 
mother to fly away. But this instinct retained by our 
chickens has become useless under domestication, for 
the mother-hen has almost lost by disuse the power of 
flight. 
Hence, we may conclude, that domestic instincts have 
been acquired and natural instincts have been lost partly 
by habit, and partly by man selecting and accumulating 
during successive generations, peculiar mental habits 
and actions, which at first appeared from what we must 
in our ignorance call an accident. In some cases com¬ 
pulsory habit alone has sufliced to produce such inhe¬ 
rited mental changes; in other cases compulsory habit 
has done nothing, and all has been the result of selec¬ 
tion, pursued both methodically and unconsciously; but 
in most cases, probably, habit and selection have acted 
together. 
We shall, perhaps, best understand how instincts in a 
state of nature have become modified by selection, by 
considering a few cases. I will select only three, out of 
the several which I shall have to discuss in my future 
work,—namely, the instinct which leads the cuckoo to 
lay her eggs in other birds’ nests; the slave-making 
instinct of certain ants; and the comb-making power of 
the hive-bee; these two latter instincts have generally, 
and most justly, been ranked by naturalists as the most 
wonderful of all known instincts. 
It is now commonly admitted that the more imme¬ 
diate and final cause of the cuckoo’s instinct is, that 
