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individual from another, we may see at once from consider 
ing the difficulty which is felt in the case of twins who 
are sometimes almost if not altogether indistinguishable. 
If tricks of manner impaired the utility of an hereditary 
action, they would scarcely go unnoticed and unrebuked. 
In the animal world the instruction of parents supplements 
the deficiency of instinctive action, just as the trainer’s 
supervision does in the case of domesticated animals. 
The attention of Mr. Romanes was first drawn to this 
point by observing how such tricks were suppressed by 
those who had the care of children. In none of these 
cases could tricks of manner present material for the evo 
lution of new instincts by means of Natural Selection. 
The difference of disposition and of habit is quoted in 
confirmation of this argument. If such differences arose 
without any cause, in a perfectly casual way, without any 
act of intelligence, without any attempt to adaptation,— 
then they might become the material for unintelligent and 
non-adaptive habits which, being inherited, would become 
a blind foolish instinct. But is this so ? “ One ant will 
let itself be killed rather than let go the pupa which it 
carries ; another will let it fall, and run away.” One is a 
hero and a martyr; the other is a coward and a poltroon. 
But both acts have an end to fulfil ; both acts are per 
formed with a very definite purpose. In the one case, 
the ant tries to save the pupa ; in the other case, the ant 
tries to save itself; and while both are intelligent enough 
to have a purpose, unfortunately it is only the coward 
who accomplishes the end that it has in view. It would 
surely be bitter irony to say that the ant which relin 
quishes a pupa acts on blind instinct. Shakespeare intends 
to be thus ironical when he makes Falstaff say, 
“ Instinct is a great matter ; I was a coward on instinct.” 
—{King Henry IV. Part act ii., sc. 4.)