es of laying
down under certain circumstances a rough wall in its proper place
between two just-commenced cells, is important, as it bears on a fact,
which seems at first subversive of the foregoing theory; namely, that
the cells on the extreme margin of wasp-combs are sometimes strictly
hexagonal; but I have not space here to enter on this subject. Nor does
there seem to me any great difficulty in a single insect (as in the case
of a queen-wasp) making hexagonal cells, if she were to work alternately
on the inside and outside of two or three cells commenced at the same
time, always standing at the proper relative distance from the parts
of the cells just begun, sweeping spheres or cylinders, and building up
intermediate planes.

As natural selection acts only by the accumulation of slight
modifications of structure or instinct, each profitable to the
individual under its conditions of life, it may reasonably be asked, how
a long and graduated succession of modified architectural instincts,
all tending towards the present perfect plan of construction, could
have profited the progenitors of the hive-bee? I think the answer is not
difficult: cells constructed like those of the bee or the wasp gain in
strength, and save much in labour and space, and in the materials of
which they are constructed. With respect to the formation of wax, it is
known that bees are often hard pressed to get sufficient nectar; and
I am informed by Mr. Tegetmeier that it has been experimentally proved
that from twelve to fifteen pounds of dry sugar are consumed by a
hive of bees for the secretion of a pound of wax; so that a prodigious
quantity of fluid nectar must be collected and consumed by the bees in
a hive for the secretion of the wax necessary for the construction
of their combs. Moreover, many bees have to remain idle for many days
during the process of secretion. A large store of honey is indispensable
to support a large stock of bees during the winter; and the security
of the hive is known mainly to depend on a large number of bees being
supported. Hence the saving of wax by largely saving honey, and the
time consumed in collecting the honey, must be an important element of
success any family of bees. Of course the success of the species may
be dependent on the number of its enemies, or parasites, or on quite
distinct causes, and so be altogether independent of the quantity of
honey which the bees can collect. But let us suppose that thi