174 ANIMAL INTELLIGENCE. 



This statement having fully borne out his theory, Mr. 

 Darwin continues : 



Hence we may safely conclude that, if we could slightly 

 modify the instincts already possessed by the Melipona, and in 

 themselves not very Wonderful, this bee would make a structure 

 as wonderfully perfect as that of the hive-bee. We must sup- 

 pose the Melipona to have the power of forming her cells truly 

 spherical, and of equal sizes ; and this would not be very sur- 

 prising, seeing that she already does so to a certain extent, and 

 seeing what perfectly cylindrical burrows many insects make in 

 wood, apparently by turning round on a fixed point. 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 

 acciirately at what distance to stand from her fellow-labourers 

 when several are making their spheres ; but she is already so 

 far able 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 instinct, 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. 1 



Mr. Darwin next tested this theory by the experiment 

 of introducing into beehives plates of wax, and observing 

 that the bees worked upon these plates just as the theory 

 required. That is to say, they made their cells by ex- 

 cavating a number of little circular pits at equal distances 

 from one another, so that by the time the pits had ac- 

 quired the width of an ordinary cell, the sides of the pits 

 intersected. As soon as this occurred the bees ceased to 

 excavate, and instead began to build up flat walls of wax 

 on the lines of intersection. Other experiments with very 

 thin plates of vermilion-coloured wax showed that the 

 bees all worked at about the same rate, and on opposite 

 sides of the plates, so that the common bottoms of any 

 two opposite pits were flat. These flat bottoms 'were 

 situated, as far as the eye could judge, exactly along the 

 planes of imaginary intersection between the basins on 

 the opposite sides of the ridge of wax ; ' so that if the 



} Origin of Sjjrciex, ' Cell-making Instinct.' 



