ld gladly have gone farther into the
question, had I possessed the necessary apparatus. But I have not, I
never have had and of course I never shall have the resources which are
so useful to the seeker. These are reserved for the clever people who
care more for lucrative posts than for fair truths. Let us continue,
however, within the measure which the poverty of my means permits.

When duly fattened, the grubs of the flesh flies go underground to
transform themselves into pupae. The burial is intended, obviously, to
give the worm the tranquillity necessary for the metamorphosis. Let us
add that another object of the descent is to avoid the importunities
of the light. The maggot isolates itself to the best of its power and
withdraws from the garish day before contracting into a little keg.
In ordinary conditions, with a loose soil, it goes hardly lower than a
hand's breadth down, for provision has to be made for the difficulties
of the return to the surface when the insect, now full grown, is impeded
by its delicate fly wings. The grub, therefore, deems itself suitably
isolated at a moderate depth. Sideways, the layer that shields it from
the light is of indefinite thickness; upwards, it measures about four
inches. Behind this screen reigns utter darkness, the buried one's
delight. This is capital.

What would happen if, by an artifice, the sideward layer were nowhere
thick enough to satisfy the grub? Now, this time, I have the wherewithal
to solve the problem, in the shape of a big glass tube, open at both
ends, about three feet long and less than an inch wide. I use it to blow
the flame of hydrogen in the little chemistry lessons which I give my
children.

I close one end with a cork and fill the tube with fine, dry, sifted
sand. On the surface of this long column, suspended perpendicularly in a
corner of my study, I install some twenty Sarcophaga grubs, feeding
them with meat. A similar preparation is repeated in a wider jar, with
a mouth as broad as one's hand. When they are big enough, the grubs in
either apparatus will go down to the depth that suits them. There is no
more to be done but to leave them to their own devices.

The worms at last bury themselves and harden into pupae. This is the
moment to consult the two apparatus. The jar gives me the answer which
I should have obtained in the open fields. Four inches down, or
thereabouts, the worms have found a quiet lodging, protected above
by the layer through