emergence from the cocoon, take place in the same order? Does the
evolution of the elder wait upon that of the younger, so that each
may give those who would bar his passage time to effect their
deliverance and to leave the road clear? I very much fear that logic
has carried your deductions beyond the bounds of reality. Rationally
speaking, my dear sir, nothing could be more accurate than your
inferences; and yet we must forgo the theory of the strange inversion
which you suggest. None of the Bramble-bees with whom I have
experimented behaves after that fashion. I know nothing personal
about Odynerus rubicola, who appears to be a stranger in my district;
but, as the method of leaving must be almost the same when the
habitation is exactly similar, it is enough, I think, to experiment
with some of the bramble-dwellers in order to learn the history of
the rest.

My studies will, by preference, bear upon the Three-pronged Osmia,
who lends herself more readily to laboratory experiments, both
because she is stronger and because the same stalk will contain a
goodly number of her cells. The first fact to be ascertained is the
order of hatching. I take a glass tube, closed at one end, open at
the other and of a diameter similar to that of the Osmia's tunnel. In
this I place, one above the other, exactly in their natural order,
the ten cocoons, or thereabouts, which I extract from a stump of
bramble. The operation is performed in winter. The larvae, at that
time, have long been enveloped in their silken case. To separate the
cocoons from one another, I employ artificial partitions consisting
of little round disks of sorghum, or Indian millet, about half a
centimetre thick. (About one-fifth of an inch.--Translator's Note.)
This is a white pith, divested of its fibrous wrapper and easy for
the Osmia's mandibles to attack. My diaphragms are much thicker than