down at the bottom of the gallery; the latest arrival ends it at the
top; and those in between follow upon one another, according to age,
from base to apex.

Let us next observe that there is no room in the shaft for two Osmiae
at a time on the same level, for each cocoon fills up the storey, the
keg that belongs to it, without leaving any vacant space; let us also
remark that, when they attain the stage of perfection, the Osmiae
must all emerge from the shaft by the only orifice which the bramble-
stem boasts, the orifice at the top. There is here but one obstacle,
easy to overcome: a plug of glued pith, of which the insect's
mandibles make short work. Down below, the stalk offers no ready
outlet; besides, it is prolonged underground indefinitely by the
roots. Everywhere else is the ligneous fence, generally too hard and
thick to break through. It is inevitable therefore that all the
Osmiae, when the time comes to quit their dwelling, should go out by
the top; and, as the narrowness of the shaft bars the passage of the
preceding insect as long as the next insect, the one above it,
remains in position, the removal must begin at the top, extend from
cell to cell and end at the bottom. Consequently, the order of exit
is the converse to the order of birth: the younger Osmiae leave the
nest first, their elders leave it last.

The oldest, that is to say, the bottom one, was the first to finish
her supply of honey and to spin her cocoon. Taking precedence of all
her sisters in the whole series of her actions, she was the first to
burst her silken bag and to destroy the ceiling that closes her room:
at least, that is what the logic of the situation takes for granted.
In her anxiety to get out, how will she set about her release? The
way is blocked by the nearest cocoons, as yet intact. To clear