We must suppose the Melipona to arrange her cells in level layers, as she already does her cylindrical cells; and we must further suppose, and this is the greatest difficulty, that she can somehow judge accurately at what distance 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 to a certain extent; and then she unites the points of intersection by perfectly flat surfaces.
By such modifications of instincts which in themselves are 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.