to
stand from her fellow-labourers when several are making their spheres;
but she is already so far enabled to judge of distance, that she always
describes her spheres so as to intersect largely; and then she unites
the points of intersection by perfectly flat surfaces. We have further
to suppose, but this is no difficulty, that after hexagonal prisms have
been formed by the intersection of adjoining spheres in the same layer,
she can prolong the hexagon to any length requisite to hold the stock of
honey; in the same way as the rude humble-bee adds cylinders of wax
to the circular mouths of her old cocoons. By such modifications of
instincts in themselves not very wonderful,--hardly more wonderful than
those which guide a bird to make its nest,--I believe that the hive-bee
has acquired, through natural selection, her inimitable architectural
powers.

But this theory can be tested by experiment. Following the example of
Mr. Tegetmeier, I separated two combs, and put between them a long,
thick, square strip of wax: the bees instantly began to excavate minute
circular pits in it; and as they deepened these little pits, they made
them wider and wider until they were converted into shallow basins,
appearing to the eye perfectly true or parts of a sphere, and of about
the diameter of a cell. It was most interesting to me to observe that
wherever several bees had begun to excavate these basins near together,
they had begun their work at such a distance from each other, that by
the time the basins had acquired the above stated width (i.e. about the
width of an ordinary cell), and were in depth about one sixth of the
diameter of the sphere of which they formed a part, the rims of the
basins intersected or broke into each other. As soon as this occurred,
the bees ceased to excavate, and began to build up flat walls of wax
on the lines of intersection between the basins, so that each hexagonal
prism was built upon the festooned edge of a smooth basin, instead of on
the straight edges of a three-sided pyramid as in the case of ordinary
cells.

I then put into the hive, instead of a thick, square piece of wax, a
thin and narrow, knife-edged ridge, coloured with vermilion. The bees
instantly began on both sides to excavate little basins near to each
other, in the same way as before; but the ridge of wax was so thin, that
the bottoms of the basins, if they had been excavated to the same depth
as in the former experiment, would have