206 SPECIAL INSTINCTS. [CHAP. VIIL 



presence of adjoining cells ; and the following view may, perhaps, 

 be considered only as a modification of his theory. Let us look 

 to the great principle of gradation, and see whether Nature does 

 not reveal to us her method of work. At one end of a short 

 series we have humble-bees, which use their old cocoons to hold 

 honey, sometimes adding to them short tubes of wax, and likewise 

 making separate and very irregular rounded cells of wax. At the 

 other end of the series we have the cells of the hive-bee, placed in 

 a double layer: each cell, as is well known, is an hexagonal 

 prism, with the basal edges of its six sides bevelled so as to join 

 an inverted pyramid, of three rhombs. These rhombs have certain 

 angles, and the three which form the pyramidal base of a single 

 cell on one side of the comb enter into the composition of the 

 bases of three adjoining cells on the opposite side. In the series 

 between the extreme perfection of the cells of the hive-bee and 

 the simplicity of those of the humble-bee we have the cells of the 

 Mexican Melipona domestica, carefully described and figured by 

 Pierre Huber. The Melipona itself is intermediate in structure 

 between the hive and humble bee, but more nearly related to the 

 latter ; it forms a nearly regular waxen comb of cylindrical cells, 

 in which the young are hatched, and, in addition, some large cells 

 of wax for holding honey. These latter cells are nearly spherical 

 and of nearly equal sizes, and are aggregated into an irregular 

 mass. But the important point to notice is, that these cells are 

 always made at that degree of nearness to each other that they 

 would have intersected or broken into each other if the spheres 

 had been completed; but this is never permitted, the bees 

 building perfectly flat walls of wax between the spheres which 

 thus tend to intersect. Hence, each cell consists of an outer 

 spherical portion, and of two, three, or more flat surfaces, according 

 as the cell adjoins two, three, or more other cells. When one cell 

 rests on three other cells, which, from the spheres being nearly of 

 the same size, is very frequently and necessarily the case, the 

 three flat surfaces are united into a pyramid ; and this pyramid, 

 as Huber has remarked, is manifestly a gross imitation of the 

 three-sided pyramidal base of the cell of the hive-bee. As in the 

 cells of the hive -bee, so here, the three plane surfaces in any one 

 cell necessarily enter into the construction of three adjoining cells. 

 It is obvious that the Melipona saves wax, and what is more 

 important, labour, by this manner of building ; for the flat walls 

 between the adjoining cells are not double, but are of the same 

 thickness as the outer spherical portions, and yet each flat portion 

 forms a part of two cells. 



Reflecting on this case, it occurred to me that if the Melipona 

 had made its spheres at some given distance from each other, and 

 had made them of equal sizes and had arranged them symmetrically 



