found the spot
where the sting was most effectual; and the habit once formed became a
true instinct. Transitions from one method of operation to the other,
intermediary changes, sufficed to bolster up these sweeping assertions.
In a letter of the 16th of April, 1881, he asks G.J. Romanes to consider
the problem:

"I do not know," he says "whether you will discuss in your book on the
mind of animals any of the more complex and wonderful instincts. It is
unsatisfactory work, as there can be no fossilised instincts, and the
sole guide is their state in other members of the same order, and mere
PROBABILITY.

"But if you do discuss any (and it will perhaps be expected of you), I
should think that you could not select a better case than that of
the sand-wasps which paralyse their prey as described by Fabre in his
wonderful paper in the 'Anales des sciences naturelles,' and since
amplified in his admirable 'Souvenirs...'"

I thank you, O illustrious master, for your eulogistic expressions,
proving the keen interest which you took in my studies of instinct, no
ungrateful task--far from it--when we tackle it as it should be tackled:
from the front, with the aid of facts, and not from the flank, with
the aid of arguments. Arguments are here out of place, if we wish to
maintain our position in the light. Besides, where would they lead us?
To evoking the instincts of bygone ages, which have not been preserved
by fossilization? Any such appeal to the dim and distant past is quite
unnecessary, if we wish for variations of instinct, leading by degrees,
according to you, from one instinct to another; the present world offers
us plenty.

Each operator has her particular method, her particular kind of game,
her particular points of attack and tricks of fence; but in the midst
of this variety of talents we observe, immutable and predominant, the
perfect accordance of the surgery with the victim's organization and the
larva's needs. The art of one will not explain the art of another,
no less exact in the delicacy of its rules. Each operator has her own
tactics, which tolerate no apprenticeship. The Ammophila, the Scolia,
the Philanthus and the others all tell us the same thing: none can
leave descendants if she be not from the outset the skilful paralyser or
slayer that she is to-day. The "almost" is impracticable when the future
of the race is at stake. What would have become of the first-born mammal
but for its perfect instinct of