I like that “is said to.”  Probably the young bird would deny indignantly that he was alarmed, and would explain that he was only going away because he suddenly remembered that he had an engagement on the croquet lawn, or that he had forgotten his umbrella.  But whether he alarms them or not, the fact remains that the caterpillar of the puss-moth does make faces at young birds; and we may be pretty sure that, even if he began the practice in self-defence, the habit is one that has grown on him.  Indeed, I can see him actually looking out for a thrush’s nest, and then climbing up to it, popping his head over the edge suddenly and making a face.  Probably, too, the mother birds frighten their young ones by telling them that, if they aren’t good, the puss-moth caterpillar will be after them; while the poor caterpillar himself, never having known a mother’s care, has had no one to tell him that if he goes on making such awful faces he will be struck like that one day.

These delvings into natural history bring back my youth very vividly.  I never kept a puss-moth, but I had a goat-moth which ate its way out of a match-box, and as far as I remember took all the matches with it.  There were caterpillars, though, of a gentler nature who stayed with me, and of these some were obliging enough to turn into chrysalises.  Not all by any means.  A caterpillar is too modest to care about changing in public.  To conduct his metamorphosis in some quiet corner—­where he is not poked every morning to see if he is getting stiffer —­is what your caterpillar really wants.  Mine had no private life to mention.  They were as much before the world as royalty or an actress.  And even those who brought off the first event safely never emerged into the butterfly world.  Something would always happen to them.  “Have you seen my chrysalis?” we used to ask each other.  “I left him in the bathroom yesterday.”

But what I kept most successfully were minerals.  One is or is not a successful mineralogist according as one is or is not allowed a geological hammer.  I had a geological hammer.  To scour the cliffs armed with a geological hammer and a bag for specimens is to be a king among boys.  The only specimen I can remember taking with my hammer was a small piece of shin.  That was enough, however, to end my career as a successful mineralogist.  As an unsuccessful one I persevered for some months, and eventually had a collection of eighteen units.  They were put out on the bed every evening in order of size, and ranged from a large lump of Iceland spar down to a small dead periwinkle.  In those days I could have told you what granite was made of.  In those days I had over my bed a map of the geological strata of the district—­in different colours like a chocolate macaroon.  And in those days I knew my way to the Geological Museum.