particular animal is known to attack only one kind of other animal, are
we not justified in assuming that when one of them attacks a hitherto
unclassed animal, he recognises in that animal some quality which it has
in common with the hereditary enemy?"

"That is a good argument, sir," Adam went on, "but a dangerous one. If
we followed it out, it would lead us to believe that Lady Arabella is a
snake."

"We must be sure, before going to such an end, that there is no point as
yet unconsidered which would account for the unknown thing which puzzles
us."

"In what way?"

"Well, suppose the instinct works on some physical basis--for instance,
smell. If there were anything in recent juxtaposition to the attacked
which would carry the scent, surely that would supply the missing cause."

"Of course!" Adam spoke with conviction.

"Now, from what you tell me, the negro had just come from the direction
of Diana's Grove, carrying the dead snakes which the mongoose had killed
the previous morning. Might not the scent have been carried that way?"

"Of course it might, and probably was. I never thought of that. Is
there any possible way of guessing approximately how long a scent will
remain? You see, this is a natural scent, and may derive from a place
where it has been effective for thousands of years. Then, does a scent
of any kind carry with it any form or quality of another kind, either