“Of course that may be so.  But, on the other hand, should we not satisfy ourselves why he does wish to attack anything?  If for centuries, this 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 good or evil?  I ask you because one ancient name of the house lived in by the lady who was attacked by the mongoose was ’The Lair of the White Worm.’  If any of these things be so, our difficulties have multiplied indefinitely.  They may even change in kind.  We may get into moral entanglements; before we know it, we may be in the midst of a struggle between good and evil.”

Sir Nathaniel smiled gravely.

“With regard to the first question—­so far as I know, there are no fixed periods for which a scent may be active—­I think we may take it that that period does not run into thousands of years.  As to whether any moral change accompanies a physical one, I can only say that I have met no proof of the fact.  At the same time, we must remember that ‘good’ and ‘evil’ are terms so wide as to take in the whole scheme of creation, and all that is implied by them and by their mutual action and reaction.  Generally, I would say that in the scheme of a First Cause anything is possible.  So long as the inherent forces or tendencies of any one thing are veiled from us we must expect mystery.”

“There is one other question on which I should like to ask your opinion.  Suppose that there are any permanent forces appertaining to the past, what we may call ‘survivals,’ do these belong to good as well as to evil?  For instance, if the scent of the primaeval monster can so remain in proportion to the original strength, can the same be true of things of good import?”